Support multiple output paths for external assemblies, fix bug if output...

...type comes in lower case.

Damn again, not in my fork.... actually i dont have one. 

Problem: We have several ouput paths for one application, for example

tests => BuildDrop\Test
libs => BuildDrop\lib
features => BuildDrop\features

Ive extended the property VISUAL_STUDIO_OUTPUT_PATH_PROPERTY_KEY to be able to receive multiple output paths using comma separated values

Ive also fix a issue with the extension check, its allowe to have lower case outputtype. In our case library instead of Library