[firefox] Tweak click behavior in URL bar

No full selection on click or double click.

This allows me to select parts of the URL more easily.

Triple click to select all (or via shortcut CTRL+L)

See http://kb.mozillazine.org/Firefox_:_FAQs_:_About:config_Entries for
a full description of these values.
[packages] Add more tools for ubuntu

- f.lux https://justgetflux.com/
- rcm https://thoughtbot.github.io/rcm/
- zeal http://zealdocs.org/

We also introduce tags to allow `--skip-tags`

So these tools can be skiped by using th `--skip-tags` feature of ansible.

Example:

    ansible-playbook -i ~/bin/setup/hosts.ini ~/bin/setup/playbook.yml -K --skip-tags=zeal
[bootstrap] Allow custom parameters

This allows us to provide our own parameters to the bootstrap run.

*Example*

If you want to exclude some tools, use the `skip-tags` parameter:

    ./bin/setup/bootstrap.sh --skip-tags=zeal,flux
[playbook] Add `python` packages

This is needed to use the `apt` resource and to install `pip` packages.
[playbook] Use `ansible_distribution`

The `ansible_os_family` is 'Debian' on 'Ubuntu'.

Thus we use the more precise `ansible_distribution`
which is 'Ubuntu' on 'Ubuntu'.
[nvalt] Add install routine for linux `nvpy`

See
https://github.com/cpbotha/nvpy/blob/master/docs/installation.rst#ubuntu--mint--debian-step-by-step-1
[README] Update FAQ