Remove netcdf support

Sadly netcdf library is not Apache2 License compatible so we should not package it anymore.

For users who wants to use it, they can add manually [netcdf librairies](http://www.unidata.ucar.edu/software/thredds/current/netcdf-java/) in `plugins/mapper-attachments` dir and they will get the support back.

Closes #84.