#99 Singe cache management functions

[SierraBravo]

Provide means to manually enable/disable/archive/unarchive/delete a single cache. In home zones with a high cache density it's more efficient to manually keep track of status using notifications than to do daily GPX imports.

Suggestion: Add "Manage" submenu to "Cache" menu with toggle items "enable"/"disable", "archive/unarchive", menu item "Delete...". Since the Cache menu is quite crowded, the "Favorite" checkbox may be moved into the "Manage" submenu.