Make the resource manager track the md5 sums of what it installs.

The MD5sums inside the manifest of bundles are nonsense.

This commit makes sure that Krita will remember the MD5sums of the
resources it installs, and uses those same values to deinstall them.

Furthermore, it compares them to the values inside the manifest, and
will return which ones are incorrect as a warning message.

CCBUG:341752