Portal actions only within range

On the portal action page, use the player's location to enable the Hack and Link buttons if player is within 40m, disable if player is too far.

Currently, a player can double-tap and scroll to any portal and hack it. 

TODO, the recharge button should only be enabled if the player 
1) is of the same affiliation of the portal owner
2a) is within 40m of the portal, or
2b) has a portal key
3) has sufficient energy for a recharge


Unrelated, commit 4a7e2fe23d4c0d7991d7539d18d10f263ba8effd from yesterday prevents compilation. Fixing the compilation problem allows me to run the app, but it crashes immediately.