#28 Clear cache

[kaim]

Patch: Clear the cache

- adds a menu item to the 'Tools' menu name 'Clear Cache'.
- adds ClearCacheAction class to ActionPool.java and variable clearCacheAction
- adds a clearCache() method to CacheManager.java

When Lobo is running, clicking on Tools->Clear Cache should clear the cache under user_dir/.lobo/cache.

[kaim]

patch for clearing cache