Adds the ability to send a raw message (useful for json message)

[jedi4ever]

By default le_android adds the timestamp and loglevel to the message you send to logentries.

This PR adds the setSendRawMessage(boolean) function so you can remove that log prefix.
We use it for logging plain json log so parsing works correctly.

The settings is default to false so it is backwards compatible.

P.S. I think it's better to add getter/setters then to provide other constructors to the logger

[udangel-r7]

closing as merge conflict

[jedi4ever]

euh @udangel-r7 ? would you like me to rebase or implemented this in the new version?
closing it as merge conflict is a bit cryptic :)

[udangel-r7]

As nobody responded to this PR (and it seemed to became stale) I closed it. If rebase it + fix the formatting issues I am happy to merge it.

re-opening for the time being

[Mehly]

Being able to send raw data (more precisely: custom json) would be much appreciated. Currently our JSON is parsed correctly and added within the 'message' property. While this approach is already a decent benefit it would be nice to just send custom json (without having device-id, timestamp, etc. auto-attached)