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.
More update for hook docs
More info about checkpoints for manual and autoinstallation
Add contact
Add notice about list of checkpoints
Merge pull request #165 from vmoravec/hook-docs

Update hook document with content about checkpoints and autoinstallation.
NetworkServices use direct access to wicked when running in installation

inst-sys is not running systemd nor sysV init so "systemctl" cannot be
used. Direct access to network backend is used.

Currently only wicked is assumed to be used as network backend in
inst-sys.
Updated changelog
Refactoring: Turned some NetworkServices globals into constants
Added logging into NetworkServices::run_wicked
Merge pull request #169 from mchf/NI-modifications

Use wicked tool for restart / reload in installation mode
Drop icons in Wizard as it do not provide additional value (proposed by designer Kenneth Wimer)
remove more related methods
release
Merge pull request #171 from yast/drop_icons_in_wizard

Drop icons in Wizard as it do not provide additional value (proposed by ...
Merge pull request #168 from aschnell/master

- removed unreachable code path
Set network service properly when running in installation. bnc#861078
Updated changelog
Merge pull request #172 from mchf/bnc861078-net-service-detection

Set network service properly when cannot be detected during installation
Querying cached service returns false in case of exception

If querying currently cached service e.g. using is_netconfig returns
false when service detection fails. If an exception is raised it is
catched.