Connect/ Improve connection property documentation

[erinkcochran87]

This PR:

• Moves the connection property documentation out of the Connect API reference and into its own reference
• Adds additional info about each connection property to its documentation
• Adds a new guide for creating and configuring a destination using the API
• Cleans up the logic for connection object templates - moves OAuth attributes into their own include
• Adds the ability to pass on-page sidenav items to the sidenav include. Only for on-page sidenavs.