Better support for folder paths and ActiveDocument check

1. Better support for folder paths when folder names are not unique in project e.g. when project contains "Areas\Scripts\foo" and "Scripts\bar" and we are looking for "Scripts\bar" previously it would not find it because it would stop searching after "Areas\Scripts". Also add better error reporting when folder was not found.

2. Explicit error when ActiveDocument is not available. This is useful when executing transformation by right clicking file in Soulution Explorer and selecting Run custom tool when no file is open.