Improve retry method for AT+FTPPUT=1
Use strtoul instead of strtol

This change assumes that we ONLY use strtoul in the whole application. And
if we do, we can save a few hundred bytes code space.
Change timeout for waitForCREG also to 120s

This is also to avoid problems when a sim card connects for the first
time to a GPRS cell. It can take a long time to connect.