Merge pull request #2 from openalea/master

update from original
This part was raising a OSError because the .openalea/projects/oalab_examples
already existed. Using a try/except fix the issue and oalab starts.
This part was raising a OSError because the .openalea/projects/oalab_examples
already existed. Using a try/except fix the issue and oalab starts.
Trying the rebase for fix #2 and #112

Merge branch 'master' of https://github.com/cokelaer/openalea
Merge pull request #112 from cokelaer/master

fixing symlink issue
First draft to restore loader/saver approach.
Apply it to controls and part of Project
Project now use ProjectLoader for loading