Merge remote-tracking branch 'upstream/master'
Allows for request custom headers when fetching messages

* Defines new request kind ExtraHeaders
* Exposes extraHeaders property on fetch messages operations
* Modifies MessageHeader::importIMFFields for handling any headers
Fix for incorrect date() check
Merge remote-tracking branch 'upstream/master'
Merge remote-tracking branch 'upstream/master'
Fixes for PR feedback

* created separated fetchWithExtraHeaders methods, restored previous API
* removed log
* adding comments
Inhibit warnings
Revert "Inhibit warnings"

This reverts commit 6a1faddc86362635beb95fdef891dae38cbb5227.
- Removed hardcoded #warnings as mentioned in Issue #215.
- Opened individual issues for each #warning removal
Merge branch 'master' of github.com:hetissimpel/mailcore2
Merge remote-tracking branch 'upstream/master'
Enable OAuth2 Capability Check
Fixed missing constant
changing #warnings to TODO
Update to libetpan 3c99ce26d751c168c4e67813e1bedc6a6c4d1c87
Inhibit warnings
Merge pull request #221 from hetissimpel/master

Changing #warnings to TODO's.
Merge pull request #220 from CodaFi/x-oauth2-capability

Added XOAuth2 Capability.
Merge pull request #204 from thusfresh/CustomReceiveHeaders

Allows for requesting optional headers when fetching messages.
Adds automatically fetch kind when extra headers is non-NULL