NEXUS-5772: Switch to make Nx use opendesktop mime magic file
NEXUS-5772: Ability to override location of MIME database file

As it seems, the new standard does not agree on OS location for it.
Hence, added ability to override this location generally.
NEXUS-5772: Somewhat related, bump to latest 2.1.3 version

It contains some resource handling fixes, see
http://sourceforge.net/p/mime-util/code/122/
NEXUS-5772: Added UT

And it was a painful experience, as MimeUtil loves
static fields and states, and making it
"reboot" is PITA.

Also, initial implementation was actually wrong
(discovered while doing UT), as the Opendesktop
mime detector implicitly uses static/singleton
MimeUtil2 to add loaded mime entries, unless
is explicitly registered.... (and the static
one is still filled up too, so duplication
happens).

Hardly to be fixed, unless forked.
NEXUS-5772: Fix license hdr on new UT
NEXUS-5772: Undoing bump to MimeUtil 2.1.3

As this dot release seems introduces some
change (probably bugfixes, see NexusMimeTypes and
it's "hacks") wrt entry ordering.
Merge pull request #71 from sonatype/nexus-5772-opendesktop-mimemagic-file

NEXUS-5772: support opendesktop mimemagic file