Added a size argument to hex2bin.

This avoids buffer overflows and related bad things.
Grammar.
Cleaned up and documented friend request code.
Rewrore JSON load/save code.
Refactoring.
Renamed tox-weechat-json to -data.
Fixed data loading/saving.
Store unsent messages for later transmission.
Added tags to printed messages.
Refactored offline messaging.
Use Jansson _new methods instead of decrefing.
Removed unnecessary header declarations.
Added method declaration.
Implemented loading unsent messages from disk.
Mass refactor :boom: