Restructure the documentation according the new spec

Group the existing pages in the new top-level categories; each
category can be seen as a separate document and it has its own
index file.
The content of the pages was not changed, with the obvious
exception of the links between pages.

The autogenerated configuration has not been added yet to
configuration/; it will be fixed in a future commit.

At the same time, as suggested by the doc team, consistently
use only one separator in file names (dash, '-') instead of a mix
of dashes, dots and underscores. This may break even more links on
the Internet, but we are breaking them anyway by moving files.
Redirects can be set, but not in this commit.

Closes-Bug: #1706184
Change-Id: I5a10378d9da2603d617ad4193ea8d90e2afc5104

doc/source/user/mapr-plugin.rst

@@ -0,0 +1,116 @@
+MapR Distribution Plugin
+========================
+The MapR Sahara plugin allows to provision MapR clusters on
+OpenStack in an easy way and do it, quickly, conveniently and simply.
+
+Operation
+---------
+The MapR Plugin performs the following four primary functions during cluster
+creation:
+
+1. MapR components deployment - the plugin manages the deployment of the
+   required software to the target VMs
+2. Services Installation - MapR services are installed according to provided
+   roles list
+3. Services Configuration - the plugin combines default settings with user
+   provided settings
+4. Services Start - the plugin starts appropriate services according to
+   specified roles
+
+Images
+------
+The Sahara MapR plugin can make use of either minimal (operating system only)
+images or pre-populated MapR images. The base requirement for both is that the
+image is cloud-init enabled and contains a supported operating system (see
+http://maprdocs.mapr.com/home/InteropMatrix/r_os_matrix.html).
+
+The advantage of a pre-populated image is that provisioning time is reduced, as
+packages do not need to be downloaded which make up the majority of the time
+spent in the provisioning cycle. In addition, provisioning large clusters will
+put a burden on the network as packages for all nodes need to be downloaded
+from the package repository.
+
+For more information about MapR images, refer to
+https://github.com/openstack/sahara-image-elements.
+
+There are VM images provided for use with the MapR Plugin, that can also be
+built using the tools available in sahara-image-elements:
+https://s3-us-west-2.amazonaws.com/sahara-images/index.html
+
+MapR plugin needs an image to be tagged in Sahara Image Registry with
+two tags: 'mapr' and '<MapR version>' (e.g. '5.2.0.mrv2').
+
+The default username specified for these images is different for each
+distribution:
+
++--------------+------------+
+| OS           | username   |
++==============+============+
+| Ubuntu 14    | ubuntu     |
++--------------+------------+
+| CentOS 6     | cloud-user |
++--------------+------------+
+| CentOS 7     | centos     |
++--------------+------------+
+
+Hadoop Version Support
+----------------------
+The MapR plugin currently supports Hadoop 2.7.0 (5.2.0.mrv2).
+
+Cluster Validation
+------------------
+When the user creates or scales a Hadoop cluster using a mapr plugin, the
+cluster topology requested by the user is verified for consistency.
+
+Every MapR cluster must contain:
+
+* at least 1 *CLDB* process
+* exactly 1 *Webserver* process
+* odd number of *ZooKeeper* processes but not less than 1
+* *FileServer* process on every node
+* at least 1 ephemeral drive (then you need to specify the ephemeral drive in
+  the flavor not on the node group template creation) or 1 Cinder volume
+  per instance
+
+Every Hadoop cluster must contain exactly 1 *Oozie* process
+
+Every MapReduce v1 cluster must contain:
+
+* at least 1 *JobTracker* process
+* at least 1 *TaskTracker* process
+
+Every MapReduce v2 cluster must contain:
+
+* exactly 1 *ResourceManager* process
+* exactly 1 *HistoryServer* process
+* at least 1 *NodeManager* process
+
+Every Spark cluster must contain:
+
+* exactly 1 *Spark Master* process
+* exactly 1 *Spark HistoryServer* process
+* at least 1 *Spark Slave* (worker) process
+
+HBase service is considered valid if:
+
+* cluster has at least 1 *HBase-Master* process
+* cluster has at least 1 *HBase-RegionServer* process
+
+Hive service is considered valid if:
+
+* cluster has exactly 1 *HiveMetastore* process
+* cluster has exactly 1 *HiveServer2* process
+
+Hue service is considered valid if:
+
+* cluster has exactly 1 *Hue* process
+* *Hue* process resides on the same node as *HttpFS* process
+
+HttpFS service is considered valid if cluster has exactly 1 *HttpFS* process
+
+Sqoop service is considered valid if cluster has exactly 1 *Sqoop2-Server*
+process
+
+The MapR Plugin
+---------------
+For more information, please contact MapR.