@Nullable/@NotNull added to various classes
Rename class: AbstractDiagnosticFactory -> DiagnosticFactory
DiagnosticFactory exposes severity
Create proper annotation descriptors when annotation arguments don't match
'Suppress warnings' as quick fix options

If no quick fix is available a special intention is shown
Update to cli-parser 1.1.1 which supports fields inherited from superclasses
Common CLI parameters extracted into a base class
assertEqualsToFile() extracted as a common utility
Simplify test code and create expected data file if not present
FilteringMessageCollector moved out
Support '-suppress warnings'