Add API views

New urls that return a json with data
Currently this supports several urls
- Get country/cluster/subcluster/station lists (can be filtered)
- Check if a station has data/weather data (on a date)
- Retrieve latest station configuration (for any date)
Fix and add docstrings, remove debug print statement
Improved API features

Added views for number of events for a specific month, day or hour
Reduce output of lists, show only top level info, no more
Added gps coordinates to station info
Improved urls to be more logical
More date validations
Only list active stations

Add active status indication to station info
Add number of events for years and for eternity
Merge branch 'api'

Add new urls that return a json with data from the database
Explicitly use read mode when accessing database files