Manually set latitude and longitude

[nickff]

Let's add the ability to manually set latitude and longitude! It'll be swell.

[fireproofsocks]

This is trickier than it sounds, so hear me out.

Regular (current) user flow:

1. user adds address data to a page, clicks save.
2. onSave event triggers plugin: fingerprints the address, checks cache to see if we already have lat/lng coordinates
3. If we don't have the info in cache, we perform a query to Google Maps API.
4. Save the lat/lng coordinates.

If you manually add lat/lng coordinates, you could change the plugin to skip the lookup if the lat/lng TVs are not empty. However, that means that if you change the address of a page, the lat/lng won't change unless you manually delete the lat/lng each time you update the address -- this won't work if you have the TVs hidden, for example.

An un-elegant solution is to have a checkbox that can override the API lookup and allow for manual definitions. A similar low-brow solution is to use a different template for records that you wish to manually set (because only resources with certain templates trigger the map API lookups).

A more elegant solution would be this:

1. Add an address, save your page.
2. If the address lookup came from Google Maps API, you cache the lat/lng and you write the lat/lng to the TVs.
3. If the address lookup came from cache, then you don't re-write the TV values UNLESS they are empty.

This would require a "hasCacheKey" type of function in the Gmarker class. The advantage here would be that a new lookup (and thus new coordinates) would be triggered/injected each time the address was changed, and you would be free to edit the lat/lng coordinates manually after that. If you needed to reset the lat/lng coordinates to the "official" coordinates, then you would need to delete the values in the lat/lng TVs (which is only possible if the TVs are visible and not hidden).