Python API: Support for per message CRC and API split.

Python API: Support for per message CRC and API split.

These changes are incompatible with Python VPP API 1.2

There is now a new VPP Class and it can be used like:

from vpp_papi import VPP
jsonfiles = []
for root, dirnames, filenames in os.walk('../../../build-root/'):
    if root.find('install-') == -1: continue
    for filename in fnmatch.filter(filenames, '*.api.json'):
        jsonfiles.append(os.path.join(root, filename))

vpp = VPP(jsonfiles)
rv = vpp.show_version()
print('RV', rv.program.decode().rstrip('\0x00'))
vpp.disconnect()

Change-Id: Ic92d226de2cf3626e750404012247e7fc24fb7fc
Signed-off-by: Ole Troan <ot@cisco.com>