Use OPENNI2_INCLUDE64 environment variable.
(Set on windows with install from http://structure.io/openni).
updated linux installation documentation
Merge remote-tracking branch 'upstream/master' into daniel
Merge pull request #3422 from avdmitry:install_doc_update
Merge pull request #3424 from dsjolie:daniel
Typos in CMake
Merge pull request #3431 from PhilLab:patch-3