simplify: remove "hu.dwim" namespace prefix and general clen-up

* remove /documentation and /integration, may reinstate in future
* place stefil-test.asd under /test and rename system to stefil-test
* cleanup asd files
* all self-tests pass
add: IS macro allows arbitrary message and arguments describing failure

customize *ALWAYS-SHOW-FAILED-SEXP* to always show the "normal" message
add: new BIND-TO-PACKAGE arg to DEFSUITE to allow future DEFINE-TEST-PACKAGE
add: new DEFINE-TEST-PACKAGE, RUN-SUITE-TESTS and DESCRIBE-FAILED-TESTS
add: a markdown README with a basic tutorial
add: gitignore
Minor whitespace changes