Improved how breakpoints are handled when a file is reloaded and keep the editor scroll position between the file reload

Fixed OnCodeEditModified resetting breakpoints to invalid lines when a file is reloaded
Changed breakpoints that are past the end of the file after a file reload tobe automatically removed
Merge pull request #2 from fsfod/filereload-improvments

Improved modified file reload behavior
Fixed DebugBackend::RegisterScript and DebugBackend::GetScriptIndex wrongly declared as returning an unsigned int when in fact they can return -1 and fix this wrong assumption in other places