#30015 Adds new methods for activity stream, search and note threads

Adds three new methods:

- text_search() gives access to the shotgun global search 
  and auto completer.
- activity_stream_read() gives access to the actitivty stream 
  for a given Shotgun entity.
- note_thread_read() gives access to a note thread, including replies
  and attachments, via a single call.

Also corrects some minor inconsistencies in doc strings, fixes spelling
errors and adds doc strings to some of the public methods that
previously didn't have them.

Closes #90.

Author: manneohrstrom