Add sentry integration module

Module for enabling raven initializing to report to sentry.

Based on feedback from my presentation at odoo days 2014
Overwrite web error message to hide traceback from user

Inject sentry_activated into web session
Overwrite CrashManager.error QWeb template
Provide translations

Signed-off-by: Sandy Carter <sandy.carter@savoirfairelinux.com>
Skip Uncaught exception in osv which is a duplicate error
Set bzrlib as optional dependency.

Code should work without bzrlib and skip logging the revnos if lib is absent.

Git dependency kept since oca/server-tools itself is git and we would like to
know sha of sentry_logger
Don't log except_osv exceptions
Don't log SessionExpiredException and TransactionRollbackError
Exclude dispatch and dispatch_rpc frames as they contain passwords
Add warning about performance impact
Merge pull request #44 from savoirfairelinux/sentry

Add sentry integration module