assimp: fix to allow to put loaders on vectors and in general fix copy
assimp: use shared_ptr for scene
ofParameterGroup: fix nested parameter groups and memory leak, switch ofPtr to shared_ptr.
Closes #2674
ofThread: detach thread on stop if it's not being waited. Closes #2506
ofThread, change order of flags and detach to avoid potential problems
Merge branch 'master' of https://github.com/openframeworks/openFrameworks.git into rexgo