This should make much more clearer what are usable and what are not
configuration options.

When branch is provided to feed with `;` we should also replace that
with exact hash.

This fixes problem with ignored packages that were introduced by patch.
What this does is that it installs packages after patching is done. It
also first updates indexes again before installation.

Because this feature was originally split between two function but
patch_feeds had to be inserted to the middle of get_feeds I decided to
drop both and used upper repatch_feeds instead. This means that we are
no longer able to get and patch feeds separately but I think that this
separation was almost useless.

Currently we support Turris OS only with SD card on BTRFS so we should
reflect that here.

These options are selection of sensible options that were set in 4.4
config for Turris 1.x but were not in 4.14 config. This is only
temporally patch to test if this is going to work. We should later clean
this patch.

It seems that when we disable eth0 that leads to switch port 6 it causes
kernel panic on null pointer dereference. This is probably symptom of
some other error but for now we just won't disable this port and that
helps.

Previous patch was causing null pointer dereference kernel panic with
phy variant. This one hopefully should fix it.

Foris no longer uses python2 so we can drop python2 version.

This reverts commit aeaa8233.

It did not help so let's wait for some free time of kernel developer.

This should consistently expand path to compile_pkgs script no matter if
symbolic link for used or not.