Caching maps regions data about osmand

[vshcherb]

Not sure how much data is saved, I think it's reloaded each app run so it's perfectly fine to get map udpates

[brbar]

I noticed this problem when I was playing with data storage location. Once I choose Multiuser storage 2 (on SD card) everything (indexing, regions downloads) starts to work 10x times slower than you choose manually specified storage on the same sd card. In my case with that configuration the regions data was not downloaded for a minutes after opening this screen. When you select manually specified storage it took seconds to download maps regions data and the other file operations works much faster.

Additionaly, I would love to have a more convenient maps management mechanism instead of using Local maps screen which is messy.

[brbar]

created a separate issue #20010 for slow file operations problem