using boost to create GUID

git-svn-id: http://ifcplusplus.googlecode.com/svn/trunk@25 06f6d6f3-f2e0-f239-6e86-ba6a5d17d3a5
git-svn-id: http://ifcplusplus.googlecode.com/svn/trunk@26 06f6d6f3-f2e0-f239-6e86-ba6a5d17d3a5
minor changes

git-svn-id: http://ifcplusplus.googlecode.com/svn/trunk@27 06f6d6f3-f2e0-f239-6e86-ba6a5d17d3a5
git-svn-id: http://ifcplusplus.googlecode.com/svn/trunk@28 06f6d6f3-f2e0-f239-6e86-ba6a5d17d3a5
simplify half space extrusion
fix bug in subtraction of openings
added separate viewer for debugging during geometry processing

git-svn-id: http://ifcplusplus.googlecode.com/svn/trunk@29 06f6d6f3-f2e0-f239-6e86-ba6a5d17d3a5
git-svn-id: http://ifcplusplus.googlecode.com/svn/trunk@30 06f6d6f3-f2e0-f239-6e86-ba6a5d17d3a5
git-svn-id: http://ifcplusplus.googlecode.com/svn/trunk@31 06f6d6f3-f2e0-f239-6e86-ba6a5d17d3a5