updating vt-to-maec for MAEC 5.0 JSON specification

[elegantmoose]

Will Require:

1. "vt-to-maec/vt_to_maec.py" - currently outputs MAEC objects to XML, will need to be JSON
2. "vt-to-maec/virustotal_to_maec/virustotal_maec_packager.py" - currently instantiates and builds MAEC objects to fill with result data from VirusTotal API. Since the new MAEC and CybOX specifications have changed, the static code that builds and fills the resulting MAEC objects must be modified. Additionally, core MAEC and CybOX type python bindings that are found in python-maec and python-cybox must be refactored(updated).

[gtback]

Unless you want the same code to simultaneously support MAEC 4.X and MAEC 5, I'd almost recommend making an entirely new repo for this.