[FEATURE] Migrate advanced metadata

The metadata migration tool from the command controller considers
only basic metadata. If extension filemetadata is loaded, it
should import much more information from the DAM.
[BUGFIX] Improve media tag migration regex

This commit ensures that media tags like this one is also migrated:

<media 12345>Lorem</media>
Merge pull request #15 from mostwanted1976/patch-1

[BUGFIX] Improve media tag migration regex
Merge pull request #14 from fsuter/metadata

[FEATURE] Migrate advanced metadata