Add -d flag to dot-push/pull

dot-push/pull will now delete files that are on the target machine, but
not on the source machine.
Change <F2> in vimwiki to also move to column 0

Previously it used `^` which moved to the first "text" column, which
might be indented if the line above as indented. We now use `0` to move
to column 0 instead, so that the timestamps are always at the furthest
indent level (which how they have always been used).