* Create convert to record refactoring action

- modify ConvertToRecordRefactoring.checkInitialConditions() to allow
  private fields to not have a constructor and to convert the
  ICompilationUnit to CompilationUnit if fASTRoot is not specified
  plus add more specific error messages
- add RefactoringAvailabilityTester support for convert to record
- add convert to record support to RefactoringExecutionStarter and
  to RefactorActionGroup
- add necessary definitions to jdt.ui plugin.xml
- add new ConvertToRecordWizard and ConvertToRecordAction classes
- add new ConvertRecordTestsl class
- fixes #2681