Initial commit of example plugin code

from http://www.process-one.net/en/wiki/Writing_a_Tsung_plugin/

Note, does not compile, giving:

    src/tsung/ts_myclient.erl:60: field dyndata undefined in record state_rcv
    src/tsung/ts_myclient.erl:96: record dyndata undefined
    make: *** [ebin/ts_myclient.beam] Error 1