Added first cut at LoadMcStasNexus
Merge pull request #1 from trnielsen/master

First version of MaStas reader for processed NeXus data
Update LoadMcStasNexus.cpp

Improve docomentation. re #6922
use newer nexus header. re #6922
additional nexus header needed for linux. re #6922
Add unit test and wiki documentation. re #6922

Also removed compiler errors
Merge remote branch 'origin/feature/6922_mcstas'