Tile Cache should only be cleared if the saved Map Definition resource has changes in base layer

[jng]

The Tile Cache invalidation logic should be more refined. Currently saving a Map Definition will invalidate the tile cache for that layer, even if there were no changes to the base layer settings.

The Tile Cache should only be invalidated when there are changes found in the base layer section of the Map Definition. For example, adding dynamic layers to a Map Definition with tiled layers and saving that resource should not clear the tile cache as the tiles are still valid.

Steps to reproduce:

1. View any web layout containing a map definition w/ tiled layers
2. A generated folder containing the tiles should be in the defined TileCache folder
3. Perform any change to this map definition that does not affect the base layers (eg. Changing the description, adding an untiled layer, etc) and save it.
4. That generated folder is now deleted. Nothing was changed in the base layer settings so this folder (and all generated tiles within) should have remained.