Merge pull request #108 from audioscience/staging

Staging
Windows build requirement is now Visual Studio 2013 or later
Merge pull request #113 from andrew-elder/master

Windows build requirement is now Visual Studio 2013 or later
Merge pull request #115 from audioscience/staging

Update background descriptor reading
Merge pull request #117 from audioscience/staging

From staging - add external port descriptors
Merge pull request #119 from audioscience/staging

add string represention of descriptor fields
Changes utility class to a namespace
Utility now lies under avdecc_lib namespace
Merge pull request #121 from ajwlucas/staging

Replaces utility virtual class with its own namespace
Merge branch 'staging' of github.com:audioscience/avdecc-lib into staging