Fix "struct" binding in nested `sp-get` calls
Add `sp-indent-adjust-sexp` and `sp-dedent-adjust-sexp`
Add `sp-point-in-blank-sexp` and rename `sp--blank-line-p` to `sp-point-in-blank-line` to be consistent with the rest.
Refactor `sp--compare-sexps`
Some `sp-get` refactoring for more consistent style