Improved robustness of the XML parser.
Also changed XML import code to raise an exception when errors arise.
Added a 'format' field to the messages for specifying if CAN messages are standard or extended.
Display the ID of messages differently depending on if they're standard or extended messages.
GUI now outputs better error messages when loading XML files.
messageInfo elements in the XML metadata files should now have a 'size' attribute for how many bytes of payload they contain.
Fixed generation of transmit messages to account for the message format and the payload length.
Still broken when multiple fields are packed into the same byte.
Merge pull request #12 from Susurrus/master

Added a "format" to messages