Issue-379 Database update API

- get_instance() of WP_Stream_Install instead of calling check() method
Issue-379 Database update API

- Add constructor method to initiate class then call check();
- Added prompt_update() method to handle user controlled db update
Issue-379 Database update API

- Added final code documentation to class methods
Issue-379 Database update API

- Fixed correct $_REQUEST keys to check for during each stage of update routine
Issue-379 Database update API

- Replace esc_html with esc_html_e
Issue-379 Database update API

- added error_log() calls to test installing over multiple versions
- fixed bug - move the update database button to the end of the function
Issue-379 Database update API

- Moved the database user upgrade process outside of the plugin list table hook.  1st Update Database notice is still there but rest of routine lives on it's own.
merge conflicst
Code formatting
Refinement of update and redirect routines when database updates are performed
Added register_update_hook that can be used by connectors

-  Stores current connector versions and only fires callback function when version changes
Moved WP_Stream::instal() to fire on init.  Needs Stream_Admin to be loaded now
Fixed bug with query_string matching
Final bug fixes from testing - ready to send pr

- correct wp_stream_update query arg
Formating and white space
Added documentation to the new install / update methods
Improving output of admin alerts
Space police
Include text domain in localized string, remove extra space
Code formatting fixes