OTMessage: rename class to Message
OTMessage: rename files to Message.{h,c}pp
Merge pull request #399 from toxeus/renameOTMessage

OTMessage: rename to Message
Some small comment cleanups
Remove -2 as an error code

The error code is never checked.

The methods for handling the error are not implemented.

The error is unlikely to occur.

The error can be prevented by using the correct data types.
Remove references to unused error code

Was always just demoted to -1 anyway

If we really care about request numbers > int32 we'll just use int64
Merge pull request #402 from OttoAllmendinger/pr-remove-minus2

Remove -2 error code
Use OTTransactionType::SetLoadInsecure() instead of manually setting m_bLoadSecurely.

SetLoadInsecure() exists for this purpose.
Cleanup in OTLedger::UpdateContents().

* Variable bSavingAbbreviated set redudantly.
* Removed nPartialACTUALCount that is only used for an assert that
  cannot fail.
* Make nPartialRecordCount depend on bSavingAbbreviated, instead of
  replicating the logic for both.
Merge pull request #404 from benma/develop

Cleanup in OTLedger::UpdateContents()
Merge OTMeCpp back into OT_ME