package/jsoncpp: new package

Needed for upcoming Kodi pctv/filmon PVR packages:

https://github.com/kodi-pvr/pvr.pctv/blob/master/CMakeLists.txt#L11
https://github.com/kodi-pvr/pvr.filmon/blob/master/CMakeLists.txt#L11



[Thomas:
  - bump to 1.6.0
  - change the license to "Public Domain or MIT"
  - wrap Config.in help text]

Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>