Code cleanup - move preselection of expansion candidates for rollback and record into helper function - same overwrite order in rollback and record: 1. modified, 2. added - self.wlock() inside kwrepo class instead of repo.wlock()

enforce subn method via boolean switch There are only 2 patterns to choose, and so far only 1 case where kwtemplater.re_kw.subn is applied on data read from the working directory: when recording added files. With this change the code reflects more closely the boolean character of the switch and underlines the special case.