warn only once about each unknown remote configstatement
support new central config statement ecdsapublickey= and if present
and using tinc 1.1pre+ save it to hosts files.
make parsing of lines from central config case insensitiv

makes editing the central file easier, ECDSAPublicKey vs ecdsapublickey
Allow pingtest= in central config, but ignore it in client.

(May be used later to automatically build icinga config or something like this)