Better part path lookup.

Includes everything mentioned in https://github.com/le717/LDR-Importer/issues/40#issuecomment-31278726 , and uses (a slightly modified version) of the code from https://github.com/le717/LDR-Importer/issues/40#issuecomment-31279788

NEEDS TO BE TESTED ON WINDOWS AND OSX.
It should work perfectly fine on OSX, not so sure about windows.

Also, construction of the paths array should be moved, but it doesn't slow down performance much ATM.