removed "Use Automatic Configuration" option

from the installation mode dialog (the 2nd stage has been removed)

- 3.1.3
Merge pull request #88 from yast/removed_2nd_stage_option

removed "Use Automatic Configuration" option
Merge pull request #89 from kobliha/master

Removed dead code
Reporting an error (with <3/5> logs) if control file not found

- Errors from logs contain more detailed pieces of information
- See gh#yast/yast-installation#86
Removed the obsolete fallback control file
Fixed path
Removed client called from the fallback contol file (only)

- This client has been showing that a fallback control file is
  in use, removed as it will never be used again
Fixed a typo in comment
Shortened GitHub reference
Merge pull request #91 from kobliha/no_default_control_file

Removed so called 'default' control file
Add CONTRIBUTING.md

See:

  * https://github.com/blog/1184-contributing-guidelines
  * http://lists.opensuse.org/yast-devel/2013-10/msg00052.html