Suggestion: Change cache structure

[AM909]

In r5181:

Under Windows, the cache for slippy-map in the download dialog is in "%USERPROFILE%\Local Settings\Temp\JMapViewerTiles_%USER%\imageryType". For a specific imageryType (like Bing Aerial Maps), all the tiles are stored in the one directory. This makes it very difficult to manage the directory manually when necessary. It's impossible to look at it with explorer, run any DOS commands on it, etc. Clearing it out with "RD /S "Bing Aerial Maps"" took more than a day on a reasonably fast machine!

I'd like to suggest breaking these directories into a tree structure, like zoom/x1/x2/y1/, where x2 is the least significant 2 digits of the x-coordinate and x1 are the upper significant digits. y1 is the y-coordinate without it's least significant 2 digits, resulting in 100 tiles per directory.

For example, if the file is named like x.y.png, 112987.543112.png becomes 1129/87/5431/12.png