Notable changes:
* sbt-libisabelle plugin which takes care of Isabelle source management
  - no more submodules; Isabelle sources are now packaged in JAR files
  - no weird ROOTS file in the repository root
* less isabelle: flags, everybody would want to use the defaults anyway
* updating to Isabelle2016 becomes possible (future work)

Use a LetPattern

Also reenable printing of LetPattern

simplify terminatingCalls

terminatingCalls now returns calls with integers too.

IntInduction and all integer comparison rules are phased out. Instead
there is a single InequalitySplit rules which splits into (up to) 3 branches,
taking pc into account.

No more EqualitySplit for any other type, except generic types.

Isolate unused rules. Clean up Rules.

Improve QualifiedExamplesBank API

Use Grammars.default
Remove SafeRecursiveCalls