generalizing highlighting of glance-{api,registry}

Also fixed some highlights of configuration files.

Change-Id: I84358640a3f5046d752adb3987c267046da6ab04
Update storage admin guide for newly supported api(s) in HDS volume driver

* Clone Volume
* Extend Volume

Change-Id: I26715c2a0785bfa709bd49c262935b10cdfd5aa6
Merge "generalizing highlighting of glance-{api,registry}"
Merge "Update storage admin guide for newly supported api(s) in HDS volume driver"