"set shellcmdflag" and "set shell" doesn't work as expected.

It is impossible to set other shell from Directory with a space in Path
set shell=c:\s\ s\sh.exe
or
set shell="c:\s s\sh.exe"
does't work.

It is also impossible to set more than one flag or flags with a - 
set shellcmdflag=-lic

I wrote some integration test, but i can't fix all of them.
Could you look at that, please.

I also set a reference to xunit.extensions. This was needed for a Theory. (Data Driven Test)