Removed global service tests (they didn't really test anything useful)
Added a ScanInterval property to the srcML service
Updated srcml service tests to work with new sourcemonitor-based service.
Moved the GetCommonPath logic out of private methods in SrcMLFile and into a new FileHelper utility class.
Modified SourceMonitor.GetSolutionPath() so that it tries to find a solution directory that contains all of the project files referenced by the solution.