[FIX #7473] Topology checker-must not have duplicates does not work
[sextante]fix for calling SAGA under OSX
Merge pull request #506 from vinayan/fixdupes

[FIX #7473] Topology checker-must not have duplicates does not work
fix #4303
fix autodetect of saga & otb on OS X, also detect bundled grass, saga & otb
cleanup Qwt build for OS X