mainwindow: add trigger count spin box
mainwindow: add trigger delay spin box
settings: fix and enhance DMM settings

The config for the trigger source and the range must be updated
upon the measurement start. In the trigger source, there is also
"BUS" missing. So fix and enhance that. Furthermore, the maximum
for the trigger count and the samples count is not 5000 but 50000.
mainwindow: add trigger auto delay combo box
dmmcontrol: send trigger delay and count cfg to DMM
DMM_send_values: fix compilation for new settings handling

In the tool DMM_send_values we need to change everything to the
new settings handling as well.
configxml: optimize the config reading/matching

We compare the setting name while reading the xml config. It is
likely that we find the correct setting name at the next id after
finding one. If we can't find it there, then we should search
forwards from there. Otherwise, look backwards from there.