Investigate memory leaks

[xxv]

It seems as though there are some issues with the app running out of memory very quickly. This could be due to a few reasons:

• ImageCache - it's been recently revised, but no formal memory profiling has been done.
• Sync framework holding onto too much data
• a queue of items to sync that's bogging everything down
• Some bitmaps being generated somewhere, but not being recycled.

To reproduce:

1. Browse an itinerary (eg "food around MIT")
2. open a cast, view thumbnails
3. close cast
4. open another cast, view thumbnails
   etc.
5. runs out of memory fairly quickly on HTC Wildfire S

[xxv]

It appears as though the OSMDroid map tiles go crazy with downloads. Perhaps we should reevaluate using OSMDroid - this kind of instability is not going to work for this app.

[xxv]

The sync framework was completely rewritten, so it's most likely not that. My best guess is image cache.

[xxv]

it is almost certainly http://code.google.com/p/osmdroid/issues/detail?id=265

Tests with the image caching disabled showed that the error still persists.

[xxv]

Memory leak has been investigated. Will re-open with an issue to re-incorporate OSMDroid.