Add docs on task-affinity and configuring MySQL

Partially implements blueprint mistral-install-docs

Change-Id: I1859742cabaa404e25354c036e555109e045c8da

README.rst

@@ -84,6 +84,33 @@ Mistral configuration is needed for getting it work correctly either with real O
 
     auth_enable = False
 
+5. Also, configure rabbit properties: *rabbit_userid*, *rabbit_password*, *rabbit_host* in section *default*.
+
+6. Configure database. **SQLite can't be used in production.** Use *MySQL* or *PostreSQL* instead. Here are the steps how to connect *MySQL* DB to Mistral:
+
+* Make sure you have installed **mysql-server** package on your Mistral machine.
+* Install *MySQL driver* for python:
+
+    pip install mysql-python
+
+or, if you work in virtualenv, run
+
+    tox -evenv -- pip install mysql-python
+
+* Create the database and grant privileges:
+
+    mysql -u root -p
+
+    CREATE DATABASE mistral;
+    USE mistral
+    GRANT ALL ON mistral.* TO 'root'@'localhost';
+
+* Configure connection in Mistral config:
+
+    [database]
+
+    connection = mysql://root:@localhost:3306/mistral
+
 Before the first run
 --------------------
 
@@ -122,6 +149,20 @@ To run Mistral Task Executor instance perform the following command in a shell:
 
 Note that at least one Engine instance and one Executor instance should be running so that workflow tasks are processed by Mistral.
 
+If it is needed to run some tasks on specific executor then *task affinity* feature can be used to send these tasks directly to this executor. In configuration file edit section "executor" *host* property:
+
+    [executor]
+
+    host = my_favorite_executor
+
+Then start (restart) executor. Use *targets* task property to specify this executor:
+
+    ... Workflow YAML ...
+    task1:
+      ...
+      targets: ["my_favorite_executor"]
+    ... Workflow YAML ...
+
 Running Multiple Mistral Servers Under the Same Process
 -------------------------------------------------------
 To run more than one server (API, Engine, or Task Executor) on the same process, perform the following command in a shell: