Adds global API version check for microversions

Adds a check for a request that the version requested is within the
global API version range supported by the REST API. Both the minimum
and maximum are currently set to "2.1". The maximum will be increased
everytime an API change is made.

Also sets up some template/doc files for clearly documenting
the REST API changes with each microversion increment.

Partially implements blueprint api-microversions

Change-Id: Ie7fdb2928d957c03ed788c2ddd29fe798c645fce
Merge "Adds global API version check for microversions"