elaborate mission statement

gathered my thoughts around LispEA's purpose and character
to elaborate a more well-defined mission-statement
(so that visitors won't find a faceless project).

TODO: investigate generating README.md from meta/brainstorm.org
merge project workflow and history policy
add `box` prefix to branch policy

added `box` as an alias for the `sandbox` branch prefix,
since i like the idea of keeping the root prefixes
at three characters for consistency and ease of use.

will probably consider adding `pub` as an alias for `master`
later down the line.
Merge mission statement down from 'master' into dev-meta

not sure how something from master is missing from feeder branches,
unless it predates my adoption of a formal branch workflow policy.
in any case, this also provides an opportunity to reflow
the mission statement with hard line breaks. it still baffles me
that automatic line-wrapping was ever a problem (yes, even with
archaic hard-terminals) — but then again, those were different times.
Merge mission statement from 'dev-meta' into dev

reflowed with hard line breaks.

Conflicts:
	README.md