Improve geolocation

[wbazant]

• Represent denied location with lower opacity and not clickable
• toast other errors (should be rare)
• Also enable high accuracy geolocation option

Closes #351 Closes #380 Closes #381

Makes it look like this:

[ezwelty]

@wbazant Thanks for taking this on! I think there's a bit more work to be done, though, before this can be merged. Findings from my testing:

• If location is denied, the button goes grey but the orange dot is nevertheless added at coordinates (0, 0). The orange dot should not appear in this case.
• Once the button is grey, it cannot be pressed again, even if location services have since been enabled. A full refresh is then required in order to try again. I would suggest leaving the button active, so that the user can retry, and display an error when it fails. This is the behavior of the current mobile app, which shows "Locating you", then "We could not determine your location. Either signals are too weak or location services are turned off" (https://github.com/falling-fruit/falling-fruit-mobile/blob/b13144202ace75b41815424cdcfc8bed65b72989/src/coffee/search.coffee#L195). If we can differentiate between timeout and location services being off, even better.

[wbazant]

@ezwelty thanks, fixed the bug!

The browsers don't let the site to display the prompt again, the user has to change settings (and is informed they might need to refresh.). The verbiage I'm trying to go for in the error message tries to reconcile two kinds of situations possible:

• user's intention matches settings: someone just clicked "Deny" and they know they don't want location
• user's intention does not match the settings: #377 or someone got their browser into a weird state

and will probably need to be translated eventually.

[ezwelty]

@wbazant I like it! One more small thing:

the user has to change settings (and is informed they might need to refresh)

Clicking on the greyed out icon with help cursor does not mention refresh, even though this is required for it to work after updating browser settings. Should the help message be changed to?:

"Permission to access location was denied. To enable geolocation, check browser settings and refresh the page."

[wbazant]

Sure! "check browser settings and refresh the page" is a potentially confusing mix of vague and specific, so I propose "Permission to use your location was denied. To enable geolocation, please allow location sharing in your browser settings and refresh the page.".