Merge pull request #347 from andresteingress/documentation

Documentation for ExpandoMetaClass
GROOVY-6268: minor fixes in the lambda section
GROOVY-6608 fix NPE
GROOVY-6268: use a warning block
GROOVY-6268: add a TBD section for the JSON support
two step fix typo
fix typo step two of two
GROOVY-6330: Groovy not checking generics information correctly for covariant methods implementing interfaces
GROOVY-6330: Groovy not checking generics information correctly for covariant methods implementing interfaces (fix stray legacy test)
formatting
temporarily disable test
Merge pull request #348 from andresteingress/documentation

Documentation for Categories/methodMissing/propertyMissing
GROOVY-6268: logical operators
GROOVY-6546: fixed test cases