- Since we supports plugin bases now, lets use shorter name and rename
"file-exporter" to just "file".
- this patch updates the help message and docstring for connection string
for "file-exporter"/"file" plugin
- TaskExporter located in the task module, so it is no need to store word
"Task" in the class name
Change-Id: Ic8a9a765e7365ff108c88a67995b9bf26736e54e