Merge pull request #103 from mnjuhn/master

Changes so that entire scenario can be inserted into DB from XML file.
Add method to get the current FD in the profile for a specified time
Move density to the base class, in order to get it serialized
Merge pull request #104 from javierhe/master

Add method to get the current FD in the profile for a specified time. Move density to base class in LinkState
Merge branch 'master' of github.com:calpath/model-objects
Merge pull request #105 from mnjuhn/master

Changes to schema, making fields optional and added check to addInputLin...
Merge branch 'master' of github.com:calpath/model-objects