Initial support for datastore in Horizon

Added datastore type and version columns in Instance Table
Added datastore type and version in Instance Details
Added appropriate Connection Examples (for each datastore type) in Instance Details

Launch Database has single dropdown with the following behavior:
- Auto select only if there's one datastore type and version
- Otherwise, enforce user to choose one
- Single dropdown uses optgroups to group versions for each datastore type

Implements: blueprint datastore-support

Author:    Michael Yu <michayu@ebaysf.com>
Co-Authored-By:    Ramashri Umale <rumale@ebaysf.com>
Change-Id: Iec3fb81e1fd85c653418b27d54b10c439fb3fa30