Now the script supports more flashing methods:
- JLink (with tockloader)
- OpenOCD (with tockloader)
- pyOCD
- Nordic DFU
- none (will produce an IntelHex file)

Also merged the contributions from:
- Yihui Xiong to support the Makerdiary USB dongle board
- Dennis Geurts to support Nordic DFU

Doc updated accordingly.

Imported 2 patches for Tock kernel:
- 06-add-set_vector_table_offset.patch (upstream tock/tock#1579)
- 07-nrf52-bootloader.patch (upstream tock/tock#1681)

This permits to run without persistent storage. The benefit is that the board
doesn't implement a the syscall API in Tock. The disadvantage is that rebooting
the key will reset the storage.

It seems that our internal linter is stricter than what pylint does.
Fixing the python code to make both happy and tries to fix the gap by
modifying pylintrc configuration file

Adding pylint configuration, VSCode configuration to lint on save and
make the deploy.py script compliant.

- Check that JLinkExe in properly installed
- Verify that the app is installed
- Always report failures in the exit code
- Add vscode settings for Python code formatting using Google style
- Fix issue #42 regarding tockloader version and sticky parameter

Updated the shell script that generates the certificates and the
documentation accordingly.
Caveat: now installation is a 2-step procedure, installing OS and
application are split into 2 commands.