Rename BlogRemoteService to BlogServiceRemote

Consistency :)
Extracted Blog remote interface to a protocol
Added REST blog remote and proxy

The proxy will forward the method to the REST remote when there is one
(wp.com or Jetpack) and the method is implemented. Otherwise it'll fall
back to XML-RPC
Sync options using REST when available
Map software_version directly
Include videopress in the synced options
Added assertions for syncOptionsForBlog:
Merge pull request #1788 from wordpress-mobile/issue/1521-rest-blog-options

Use REST to sync blog options