Commit part of FS#11748 by Michael Hohmuth. Adds support for automatically resuming...

Commit part of FS#11748 by Michael Hohmuth.  Adds support for automatically resuming any song that is not played to completion at any point later in time, regardless of how many intermediate tracks are played.  This is accomplished by expanding the database to record incompletely played tracks.  Currently, the feature is simply on or off, in which case all tracks automatically resume, or they do not.  The remainder of patches in the task expand this feature by allowing only certain file to automatically resume, only resuming in certain circumstances, etc but are not included until we reach agreement on what should be included.  Additionally, the manual will need to be updated once we agree on the available settings.

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@28942 a1c6a512-1295-4272-9138-f99709370657