Document and test AsciiFile

I want to use it in yast2-nfs-client to preserve comments (bnc#429326)
as it is already used elsewhere for fstab handling.
Merge pull request #176 from jsuchome/master

different check for running chef-client
- also save xorg.conf.install
Merge pull request #178 from aschnell/master

- also save xorg.conf.install
example name; better name: stub_file_reading
improved rspec style much
Merge branch 'master' into asciifile-usage

Conflicts:
	library/general/test/Makefile.am
AsciiFile: improved documentation
fixed the yardoc warnings

caused by incomplete doc comment conversion (implicit param names)
added memory detection code

see yast/yast-packager#33

- 3.1.19
Merge pull request #179 from yast/ram_detection

added memory detection code
AsciiFile spec: better descriptions

it is more fragmented now, like the result that it specifies :)
Merge pull request #149 from mvidner/asciifile-usage

Document and test AsciiFile
Add systemd socket support (bnc#853300)
Merge pull request #180 from vmoravec/add-systemd-socket

Add systemd socket support | bnc#853300
Update changes and version to 3.1.20
Merge pull request #181 from vmoravec/add-systemd-socket

Update changes and version to 3.1.20
Do not check for unit physical existence:
some LSB wrapped services are not stored in path as the typical systemd units,
it blocks them from configuration. The systemctl calls do handle the non-existence
of the systemd units fine
Adapt the testsuite output files
Update changes and version to 3.1.21