Add a new pySim-shell program

pySim-prog was nice when there were only 5 parameters on a SIM that we
could program, and where the use case was pretty limited.  Today, we
have SIM/USIM/ISIM cards with hundreds of files and even more parameters
to program.  We cannot add a command line argument for each file to
pySim-prog.

Instead, this introduces an interactive command-line shell / REPL,
in which one can navigate the file system of the card, read and update
files both in raw format and in decoded/parsed format.

The idea is primarily inspired by Henryk Ploatz' venerable
cyberflex-shell, but implemented on a more modern basis using
the cmd2 python module.

See https://lists.osmocom.org/pipermail/simtrace/2021-January/000860.html
and https://lists.osmocom.org/pipermail/simtrace/2021-February/000864.html
for some related background.

Most code by Harald Welte. Some bug fixes by Philipp Maier
have been squashed.

Change-Id: Iad117596e922223bdc1e5b956f84844b7c577e02
Related: OS#4963

contrib/jenkins.sh

@@ -13,6 +13,7 @@ virtualenv -p python3 venv --system-site-packages
 . venv/bin/activate
 pip install pytlv
 pip install pyyaml
+pip install cmd2
 
 cd pysim-testdata
 ../tests/pysim-test.sh