Show filesystem label when deleting a volume

Doesn't quite work right - needs to hook into onPrepareDialog()
otherwise deleting two volumes consecutively only shows the first one's
filesystem type correctly.
Use a custom dialog layout for volume deletion
targetSdkVersion=10 minSdkVersion=8

Android 2.3.3 - 2.3.7 still has ~10% install base, and this branch
specifically targets these users, so let's optimize for API level 10.
Fix DB crash on negative volume type

Through a bug it was possible for volumes to be inserted to the database
with type == -1. This commit fixes the bug in EDApplication.getFSIndex()
and patches the DBHelper code to drop affected volumes from the
database.

Conflicts:
	src/org/mrpdaemon/android/encdroid/DBHelper.java
Fix crash caused by previous fix

The previous fix would crash when VolumeListActivity tried to call
EDApplication.getFSIndex(null).
Handle NULL items in VolumeListAdapter.isEnabled()
DropboxFileProvider crash fix for volume in DB root

When we have a volume in the Dropbox root directory we would end up with
a crash in DropboxFileProvider.entryToFileInfo. This is because
apparently DropboxAPI.Entry has modified=null for the root directory.
Commit also fixes the relative path handling logic for the root
directory entry.

Fixes mrpdaemon/encdroid#70
encfs-java 0.8 update