added missing submit button so content can actually be saved
implemented basic i{builder,maker} packaging for BFW

This is the "standard" way of doing things, where content
gets copied into a newly created instance, in this case
created by the bfwinstance script. If time allows a further
branch off this one will try to do it the non-copy way.

The main pieces of this are:

* A 'remotes' make target that uses t.b.instance info to
  put content in a pkgstore
* src/assets.recipe which defines the content to go in
  an assets bag
* bfwinstance which creates an instance using the pkgstore data
  and instance info
* adjusting layout.html to use the bag-based assets rather than
  remotes
registered bfwinstance script, added MANIFEST.in

most likely incomplete
added missing includes and distribution target

cargo-culted from TiddlySpace

NB: `remotes` has to come after `test` for the `dist` target as
otherwise remotes are removed again
moved favicon into repository

this is a custom creation, so it belongs here
ensured special "assets" bag is not treated as a wiki

this is very much a crutch; it'd be nice to have a more generic / less
centralized mechanism to distinguish wiki and non-wiki bags - @cdent?