Rename sexp_lift_* to sexp_raise_*

This was the original name for mapping/function, but I changed it when I
was led to believe that paredit's sexp raise did not do the same.

After installing paredit.el and trying it out for myself, it appears
to be essentially the same as sexp_lift_element, so we are changing it
back!
Optimize backward top-level movement

Removes an unnecessary call to s:nearest_bracket(1) when travelling
backward

--todo
Check for blank string from visualmode()

Using setpos() to set visual marks does not change the member that
visualmode() returns, so raise (and likely others) did not work properly
when called before ever entering visual mode.
Reword comment

I thought it was a bug, but let's hedge our bets since I didn't bother
sending a patch upstream.
Documentation fixes
Add <Plug>(sexp_indent) and <Plug>(sexp_indent_top)

== shadows the mostly useless internal motion.
Merge branch 'development'

* development:
  Add <Plug>(sexp_indent) and <Plug>(sexp_indent_top)
  Documentation fixes
  Reword comment
  Check for blank string from visualmode()
  Optimize backward top-level movement
  Rename sexp_lift_* to sexp_raise_*