Add Journey model and update RecordFragment to use it

It compiles and everything seems to work still. No idea whether any of the `Parcelable` stuff actually works.
I didn't know there was a JSR for json! I know a lot of Android projects use Google's gson.

It looks like gson does a little more than `javax.json`, but in our case, this seems fine. I'd like to know if you have any input on the pros/cons of different Java json libs.