remove call to changes#Output()
remove verbose variable, always enable check
by default enable autocmd
code cleanup
only place signs, that haven't been previously placed
Revert "only place signs, that haven't been previously placed"

This reverts commit d68025c85a0d74940c7b522947175a3a9a62fd61.
catch error about undefining non-existing signs
erroneously removed parsing diff output
only undefine signs, if definition really changed
init function before calling GetDiff
skip BufWritePost autocmd, trigger on FilterReadPost command