Changed interface for model plugins to make usage of pointers and references consistent.
Added codes for tutorial belonging to VLeaf manuscript.
Something changed in modelcatalogue. I'm not sure what...

user: Roeland Merks <roeland.merks@cwi.nl>
branch 'default'
added src/TutorialCode/Tutorial0/mymodel.cpp
added src/TutorialCode/Tutorial0/mymodel.h
added src/TutorialCode/Tutorial0/mymodel.pro
added src/TutorialCode/Tutorial1/mymodel.cpp
added src/TutorialCode/Tutorial1/mymodel.h
added src/TutorialCode/Tutorial1/mymodel.pro
added src/TutorialCode/Tutorial2/mymodel.cpp
added src/TutorialCode/Tutorial2/mymodel.h
added src/TutorialCode/Tutorial2/mymodel.pro
added src/TutorialCode/Tutorial3/mymodel.cpp
added src/TutorialCode/Tutorial3/mymodel.h
added src/TutorialCode/Tutorial3/mymodel.pro
added src/TutorialCode/Tutorial4/mymodel.cpp
added src/TutorialCode/Tutorial4/mymodel.h
added src/TutorialCode/Tutorial4/mymodel.pro
added src/TutorialCode/Tutorial5/mymodel.cpp
added src/TutorialCode/Tutorial5/mymodel.h
added src/TutorialCode/Tutorial5/mymodel.pro
added src/build_models/translate_plugin.pl
changed src/VirtualLeafpar.tmpl
changed src/build_models/auxingrowthplugin.cpp
changed src/build_models/auxingrowthplugin.h
changed src/build_models/meinhardtplugin.cpp
changed src/build_models/meinhardtplugin.h
changed src/build_models/plugin_auxingrowth.pro
changed src/build_models/plugin_leaf.pro
changed src/build_models/plugin_meinhardt.pro
changed src/build_models/plugin_test.pro
changed src/cell.cpp
changed src/cellbase.cpp
changed src/cellbase.h
changed src/libplugin.pro
changed src/mesh.cpp
changed src/mesh.h
changed src/modelcatalogue.cpp
changed src/simplugin.h