Add location information to timeline

[zach-capalbo]

Photofield is great! But I sometimes forget where I've taken my photos, so I've added some code to extract the GPS coordinates from the EXIF data, and use rgeo to lookup the location. Coordinates and location are stored in the database. Unique locations are displayed on the timeline events next to the date.

I'm submitting this PR in case this is useful or helpful. Feel free to accept it or not if it aligns with the goals of the photofield project. Just some notes about this implementation:

• I've added the location to the event header for timeline view (since that's the one I usually use), but not to any of the others. Should be easy enough to do though, following the same pattern.
• rgeo is very fast and does not seem to add a noticeable delay in indexing metadata, however I have not benchmarked it
• The lookups provided by the builtin rgeo databases are not terribly precise
• The size of the photofield executable jumps to about 60MB (Windows x64) with these changes, probably due to the added geographic lookup data in rgeo. (Either that, or I'm missing some optimization or other in my build; I'm not a heavy go user)

Anyway, hope this is helpful in some way!

[SmilyOrg]

Hey, thanks a lot for contributing! I've been meaning to add something like this, just haven't gotten around to it yet!

I'll take a look at the code when I get the chance, but it looks good from a first glance.

One interesting synergy might also be with the tagging system I've been trialing in a branch. The reverse geo could be used to create tags like "city:Dublin", "country:Ireland", etc. Would make it neat for search.

[zach-capalbo]

Thanks for taking a look!! I'm not sure that I'll have much time in the next few weeks to get back to this, so please feel free to take it over and combine it with other features that you're working on. If I get some time before then, I'll make the changes to address your comments

[SmilyOrg]

@zach-capalbo I finally took some time to make the changes above! I still think the rgeo initialization time is a bit of a non-starter to be able to merge this as is, but it should be fine if it's behind a feature flag. In fact, lemme do that...