Cache scaled podcast logos, partly fixing issue #30: Improve offline and
caching behaviour

Conflicts:
	res/layout/podcast_list_item.xml
	src/net/alliknow/podcatcher/model/PodcastManager.java
	src/net/alliknow/podcatcher/model/types/Podcast.java
Merge branch 'simple' of https://github.com/salema/PodCatcher-Deluxe-Android.git into simple