Reviewing the Placement API, I noticed wrong OpenStack capitalization.
Fix the docs and some strings as well.
Change-Id: I14a2443687a0d517ece80e794e7ef0d4e165af6f
Briefly document in the Placement API reference:
a) the use of Content-Type: application/json
b) how to use microversion headers, including a link to the main
Microversions reference.
Change-Id: I60d7b9dfe4f1c50fc50eaf07a04848c220ffcf62