Doc: Separated "modules" group page from the "All Modules" page.

-they are separate and causes auto generated links to show up.
-we already have a "modules-cpp" group, so "modules" is no longer needed.
 If "modules" group is to be removed, it should be in a separate patch.

Change-Id: Ia74a945455f2765ace32dec798de45fb42b2d1d5
Reviewed-by: Martin Smith <martin.smith@digia.com>