driver pigcs: fix connection over IP with multiline answer

the parsing for multiline was incorrect, that caused exceptions when reading it.

As we read multiline answer at initialisation, that means that the whole driver was broken for IP connection.

The fix is easy: just using more advanced python slicing. Also use this technique over serial connection.
util piconfig: support IP connection

More code from pigcs, to support also IP connection.
driver pigcs test: more helpful command
Merge branch 'master' of vpn.delmic.com:odemis