medcom-wide/rootfs: Add build date information

Add the build date to the os-release info and show this information on login.

Change-Id: Ie3e4869d03aa7669012b2490f13f722e9ff06c3b
Signed-off-by: Soeren Grunewald <soeren.grunewald@avionic-design.de>
Reviewed-on: http://review.adnet.avionic-design.de/739
Reviewed-by: Alban Bedel <alban.bedel@avionic-design.de>
medcom-wide/rootfs: Enable zram based swap on bootup.

With the back-ported zram implementation we have a quite stable implementation,
which allows us to enable zram based swap. This should improve the stability of
the system under high memory load conditions.

Together with the default start, we make the zram start depend on basic.target
instead of multi-user.target. We also use only one zram block device with a
fixed size, instead of depending on the number of the cpus and the actual
system memory.

Change-Id: I7b8a7d486d4013149273c8859e10ba9850784ee4
Signed-off-by: Soeren Grunewald <soeren.grunewald@avionic-design.de>
Reviewed-on: http://review.adnet.avionic-design.de/740
Reviewed-by: Dirk Leber <dirk.leber@avionic-design.de>
medatom/rootfs: Add missing build dependency

Since we use the squashfs tools from build-tools directory, we need to make
sure that we have the tools.

Change-Id: I26d8f179c65bd83c59b447cbe2339483ceb738c4
Signed-off-by: Soeren Grunewald <soeren.grunewald@avionic-design.de>
Reviewed-on: http://review.adnet.avionic-design.de/751
Reviewed-by: Dirk Leber <dirk.leber@avionic-design.de>
tec/rootfs: Add tmux config file.

Add a configuration file for tmux, allowing us to scroll using mouse wheel
and command keybindings.

Change-Id: I134789a46781c3b8d0b9ad3686ac924c4cd66ba7
Signed-off-by: Soeren Grunewald <soeren.grunewald@avionic-design.de>
Reviewed-on: http://review.adnet.avionic-design.de/737
Reviewed-by: Dirk Leber <dirk.leber@avionic-design.de>
medcom-wide/rootfs: Add service to set sensorpads backlight

Since sx8436 driver provides a regular backlight interface, we can control the
backlight brightness. To do this we add a systemd service which loads the
configured value and sets it.

The configuration can be set via "/persist/etc/defaults/sensorpads" containing
a variable BRIGHTNESS. The valid range is 0..255.

Change-Id: I5f74beee9d413590e4fbf3c77136fc9aea4a8787
Signed-off-by: Soeren Grunewald <soeren.grunewald@avionic-design.de>
Reviewed-on: http://review.adnet.avionic-design.de/783
Reviewed-by: Alban Bedel <alban.bedel@avionic-design.de>