shinkenplugins lib: some cleaning and first factorizations.
add: x224 check.
factorized NetEcho class into tools.netecho module. + few clean.
clean obvious/useless ;)

'''
except X as e:
    assertEqual(type(e), X)
'''

hmm, yes useless ;)
though e could be a subclass of X, ok.
begin factorized do_tst into tools.tests.TestPluginBase
Add: tests: NetEcho: feature to listen on random port (better).
Fix: forgot to convert to call to version and support.
use assertRegexMatches + a message to return codes compare.
add/clean: check_x224: shorter messages + except on better place + main.
Add: x224: tests done :)