Fix various issues with import script.

[monfresh]

• Improve logic that determines whether or not a location needs to be geocoded. In addition, the location importer now checks to see if an address already exists for the location. If so, it updates that same address instead of assigning address attributes, which, unbeknown to me, actually destroyed the existing address and created a new one. The side effect of destroying the address is that it triggered the reset_location_coordinates callback, which in turn triggered the geocoding since the location no longer had coordinates.
• Invalid entries no longer prevent the entire CSV file from being saved to the database. Now, valid entries get saved, and error messages are displayed for invalid entries.
• If a CSV file doesn't have sequential IDs, the database will now save the entry with the same ID as in the CSV file. Previously, the database would assign sequential IDs, which would cause mismatches between CSV files that refer to a particular foreign key.
• Added a conditional for the touch_locations callback in organization.rb to improve performance during initial import of organizations.
• The console output that lets you know which file is being imported has been moved out of the rake task and into the EntityImporter. That way, if a file is skipped (because it's not required and is missing or empty, for example), then the console won't say that it is being imported.

Closes #336.

[coveralls]

Coverage increased (+0.0%) to 99.41% when pulling 02076ad on 336-import-fixes into f26a8e7 on master.