Date and time filtering

[ZoeAffinity]

This is tricky, because the dates and times info is incomplete for many, perhaps most, of the services.

The default value should be: start date before today, end date after tomorrow.

Can we implement an "open now?" checkbox?

Reading material:

Example: https://github.com/okfn/piati http://transparence.ambafrance-ml.org https://github.com/okfn/piati/blob/master/piati/settings/french_mfa_mali.py

Example 2: budget sliders on http://transparence.ambafrance-ml.org/projects/index.html

Examples from Affinity Bridge: http://dev.amani.peacegeeks.org/pledges http://bl.ocks.org/tnightingale/4718717

[ZoeAffinity]

No date slider or filters; we'll just put the availability date & time info into the popups.