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.
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)
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
Merge pull request #183 from vmoravec/allow-service-without-file

Do not check for service unit file | bnc#864934