dev: assorted tweaks

* provorg.el:
  - namespace change: su/provorg → provorg
  - added function (provorg/call-lob) to programmatically call lob
    functions
  - provorg/host now has an associated stack
  - made the set-dir advice to be around advice, this simplified some of
    the code
* provorg.org:
  - set `dir-dyn' buffer-wide to be yes
  - added git related utils
dev: utility to toggle org-confirm-babel-evaluate
recipes: init
todo: org-babel-tangle
util: add provorg/utils/get-var to get var in header args
dev: allow provorg/host to be set via header arg