re-tune the cache code so it's much more short-term storage
the original reason for longer term storage were the frequent error==TIMEOUT from map tiles. since these are now retried, as the stock site does, the remaining use for the cache is more short term, while panning around an area
more improvements to the data requesting
- fix idle resume, so it only occurs if the existing timer has been cancelled
- re-instate the cache, and updates for interface changes
- add a short delay between the initialisation of map data retreival, and actually starting network requests