Prompt for Unlock When Editing Diagrams in Subversion Repository

[philip-alldredge]

This is in related to and is in addition to #1132. IWorkspace.validateEdit needs to be called before making changes to diagram files. This should prompt the user to unlock the file. If validation fails, the change should not be made.

Ensure that the user is not prompted multiple times when making changes that affect multiple diagram files such as refactoring.

[philip-alldredge]

There are two SVN clients for Eclipse: subclipse and subversive. Subversive seems to have more problems than subclipse. When using subversive, an NPE occured when renaming via LTK from the grpahical editor under certain circumstances. This issue is not resolvable without changes to Xtext or Subversive. For graphical editor usages, the behavior is more reliable when using subclipse.

Prompting to unlock AADL source files and diagrams when appropriate when editing in the graphical editor is needed. However, subclipse may automatically attempt to lock files in some cases such as when refactoring elements using LTK. Unfortunately, this operation may fail if one of the files is already locked. In such cases an error is printed by subclipse to the console describing the problem.