messaging 6.x-2.0-beta6

Bug fixing and polishing. Changes since beta5:
- Reworked logging and log formatting and moved debug module to Development package
- Fixed: default filter set to default variable if empty
- Added line endings for 'Plain text' filter, #428440
- Added new API function: messaging_user_setting()
- Added wrapper for no pending messages text, by CrackWilding, #446218
- Added new API function: messaging_text_truncate(), from sms module
- Reworked SMS formatting, removed text limit, #390438
- Fixed: messaging_phpmailer does not use passed headers, by jmcclelland, #363001
- Added table and field descriptions to schema, #429184