refactor out writting sysconfig
use sysconfig class also on other place for writing
add ability to read sysconfig
add test for reading
make reading from system class method
make test more robust
remove useless import
make writing options less confusing
Add explenation for registering agent
use better method name
Merge pull request #190 from yast/bootloader_module_cleanup2

Refactor out sysconfig handling