reorganize documentation home page

[David TARDIVEL]

The home page requires a new organisation of sections to be more readable for new beginners on Watcher.

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/268086
Committed: https://git.openstack.org/cgit/openstack/watcher/commit/?id=eaed6500008a296162b310b55634d3d1c9526917
Submitter: Jenkins
Branch: master

commit eaed6500008a296162b310b55634d3d1c9526917
Author: David TARDIVEL <email address hidden>
Date: Fri Jan 15 12:30:17 2016 +0100

    Refactor Commands section

    Rename this section to 'Watcher Manual Pages' and add man RST
    files.

    Partial-Bug: #1535244
    Change-Id: I1c890c8d053238aa568075d844f97b1e4289adcb

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/268137
Committed: https://git.openstack.org/cgit/openstack/watcher/commit/?id=c8096c614802b110dc268567909dbe869063c7a1
Submitter: Jenkins
Branch: master

commit c8096c614802b110dc268567909dbe869063c7a1
Author: David TARDIVEL <email address hidden>
Date: Fri Jan 15 14:43:22 2016 +0100

    Fix 'Module index' broken HTTP link

    'Module Index' link points to HTML doc generated from source/api
    RST files. These RST files are generated by pbr, by setting the
    parameter 'autodoc_index_modules' to True.

    Partial-Bug: #1535244
    Change-Id: Ifceb5a140599d3968ea3d353b12c0bbe99d955e6

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/268167
Committed: https://git.openstack.org/cgit/openstack/watcher/commit/?id=63d950090414b46bdcfbe81db72763b935579845
Submitter: Jenkins
Branch: master

commit 63d950090414b46bdcfbe81db72763b935579845
Author: David TARDIVEL <email address hidden>
Date: Fri Jan 15 15:39:50 2016 +0100

    Re-organize the Wacher documentation Home Page

    Change the title of the page.
    Create a 'Getting Started' section.
    Create a 'Plugins' section.
    Add links to related source code repositories.
    Fix bad link to watcher client installation doc.

    Change-Id: Ie0548149751d53b5fca235da69798dd0d333b14c
    Partial-Bug: #1535244