Be consistent in how board docs are named and move all to index.rst.
This will make the URL to the board documentation predictable and easier
to remember.
Signed-off-by: Anas Nashif <anas.nashif@intel.com>
The phrase "Zephyr applications use the ..." in many boards and
inconsistently. This is just to say what is the board identify is.
Signed-off-by: Anas Nashif <anas.nashif@intel.com>