Increase next version from 1.1.1 to 1.2.0

This seems like a good idea with the TLA Tools update and other major
changes (and also lets me safely make another big change).

build.gradle

@@ -7,7 +7,7 @@ plugins {
 	id "de.undercouch.download" version "5.6.0"
 }
 
-project.version = '1.1.1-SNAPSHOT'
+project.version = '1.2.0-SNAPSHOT'
 project.group = 'de.hhu.stups'
 
 final isSnapshot = project.version.endsWith("-SNAPSHOT")