Fixes extension list / enable /disable not working when extension source not in root directory.

Signed-off-by: Rack Lin <racklin@gmail.com>
rewrite configM4Exists and lookupDirectories at caller side.

Signed-off-by: Rack Lin <racklin@gmail.com>
Merge pull request #408 from racklin/bugfix/ext_manage

Fixes extension list / enable /disable issues.