BP Types: make it possible to manage BP Types from the WP Admin

• Introduces functions to handle BP Types insertion, modification and deletion.
• Introduces a new JavaScript file to customize the default WP Terms Administration screens.
• Introduces the BP_Admin_Types class to make it possible to manage any BP Types.
• Adds the Member type's Administration screens.

Props mercime, DJPaul, dcavins, boonebgorges, tw2113, sbrajesh

See #7179
Fixes #7181