Silently ignores failures while downloading images

It seems some large icons (b200) are missing from yr.no symbols.
Thus trying to download them fails and causes the app to be unusable
for the cities using them.

Now the app will silenttly ignore the images download failures and
will use a smaller icon instead (b100) if available.

The Image using the large icons is made smaller.

Change-Id: Iaefe5f7ef85fe0d985d26873083045e44f944a17
Reviewed-by: Jens Bache-Wiig <jens.bache-wiig@digia.com>