NEXUS-5772: support opendesktop mimemagic file

Seems some OSes started using new MIME magic database format (a file enlisting magic entries) that is not compatible with "classic" one, the OpenDesktop standard.

MimeUtil2 had support for this, but the "switch" has to happen programatically (we cannot enable this or that).

Changes:
* added property to swtich to opendesktop mode (parser)
* added property to override OS mime.magic (or mime.cache in OD case) file location, as OD file locations seems different
* modified OpendesktopMimeDetector to "use the file or die", as it has some strange fallbacks and would cause misleading error messages

Issue:
https://issues.sonatype.org/browse/NEXUS-5772

CI
https://bamboo.zion.sonatype.com/browse/NX-OSSF30