Additional documentation for type inference
   * least upper bound
   * instanceof inference
Add Peter Ledbrook to the contributors
Fix wrong include for pattern variants
Reserve sections of user guide to work on.
Set IDEA language level to 1.6 and JDK name to 1.8
Merge pull request #459 from pledbrook/doc-patch-03

Reserve sections of user guide to work on.
additional utility methods
GROOVY-6887: AutoClone issue with CompileStatic