Filter projects in create observation workflow based on end date

[mo-nathan]

Projects that have passed their end date should not show up in the "Create Observation" workflow. If you are an admin for the project it might make sense for "expired" projects to show up when you edit an observation. Alternatively the admin could tweak the end date if they really need to add observations after the end date. However, I think we can also wait for a real use case of that. This might ultimately turn into giving projects a more complex life cycle, but I don't think we have enough clarity yet on how folks want to use projects yet.