Add initial 1.x -> 2.x migration guide
Add initial 1.x -> 2.x migration guide

It should be used to document breaking API changes.

Change-Id: I70e8f0a12461aa2a35aeaf9914675d2d6dfb8c4b

eclipsesource/tabris-js,eclipsesource/tabris-js,eclipsesource/tabris-js