Added test case for Product
Little Product refactoring
Extended Product test

- Run during installation
- Run during update
- Run during AutoYast Config
Fixed behavior for AutoYast Config

- On a running system, name and version are read from /etc/os-release
Refactoring
Refactored OSRelease.rb

- Checking whether os-release is supported moved to a separate function
- Path to os-release file moved to constant
Refactored Product library

- Supported way of getting the product info has been changed to rely on
  existency of the info source file
- Adapted test case
Added missing makefile
Ruby way of setting a variable if .nil?
os_release_exsits? instead of supported?

- No preference, maybe a bit more understandable to external contributor
- Comes from code review
New changes file entry and new version
Merge pull request #213 from kobliha/installed_product_version

Changed way how to determine THE PRODUCT bnc#871261