Allow multiple inputs in location filters

[svoboond]

Add option to search for locations by multiple countries/counties/municipalities as discussed in #65.

[andersfi]

Also, remember the selection by "locationType" Default should be 'lake centroid'

[ninsbl]

For lake name and id text / table input is useful. For administrative units the current combo boxes - just with multiple selection - and the 'drill-down' functionality are pretty good!

[svoboond]

This issue has a lower priority, changing milestone.