initial commit for advanced hooks (fate#314132)
fixed variable name
sort the scripts, ask if the script fails
updated hook documentation
moved script searching to a separate function
updated documentation
merge stage and step (step is sufficient)
added docu link
updated hook script format
added new hooks to Wagon clients (fate#314132)
fixed syntax error in Wagon.ycp
*.spec - include /var/lib/YaST2/wagon/hooks/ in the RPM package
updated hoo script name schema
added doc/Migration_Hooks.md
reformatted Migration_Hooks.md (break long lines)
Added online link to Migration_Hooks.md
package doc/Migration_Hooks.md file
Migration_Hooks.md - updated example
Wagon.ycp - fixed example and the docu link
display "progress" in UI when running hooks