tc: add options to allow for no popup windows

The FVP conveniently pops up a status and a graphical window as well as
a new terminal window for every UART interface. However, these windows
are quite clunky (can't copy from them), half the time just one is
needed, and using a headless machine is completely impossible. Add
--visualisation to get rid of the graphical windows when they are not
needed and --telnet to disable the terminals and let the user connect
with their preferred (telnet) client.  UARTs will start at port 5000 and
count up. The FVP is smart enough to detect which ports are taken up and
use higher port numbers so having many runs at the same time is also
possible. Port numbers should even be stable as long as just 1 out of N
running FVPs is killed and restarted.  This allows for easy to use
headless runs.

Also add a --debug to make debugging easier.

Signed-off-by: Boyan Karatotev <boyan.karatotev@arm.com>