fix client and session management

- BPFogBugzClient is now dumb, it doesn't maintain any session state other that the state that is set upon a successful login.
- BPBugManager is a singleton managing one client and is responsible for persisting details for future connections (url, api details, user, session).

WIP: login view and api/session management
refactor to manages 'cases' not 'bugs'
add DLog macros
add support for submitting attachments with cases

- Added BPPhotoLibrarian.
- Added added basic buttons to attach images.