two simple segments (vcscommand and linesinfo)

vcscommand is similar to fugitive but for several VCSs
linesinfo is like lineinfo but with total counts

I might try to add some docs, since these are good illustrations of

    call Pl#Theme#ReplaceSegment('fugitive:branch', 'vcscommand:branch')¬                 
    call Pl#Theme#ReplaceSegment('lineinfo', 'linesinfo:lineinfo')