Allow for re-use and more independent testing.

'sfdoc' is easier to type and resembles 'pydoc' and 'perldoc' so it's
even easier to remember.

Until TFKit is able to run tests in sandbox (instead of running tests
against installed SUT), this test will throw false positives in case
any other Shellfu modules are present.

This commit adds workaround that should be removed when new TFKit
version is installed.

Great rewrite with revamped CLI, many added features and bugfixes.

 *  New CLI optimized for simple use.  Default action is to show
    module doc in manpage viewer.

 *  Respects variable documentation.

 *  Respects module documentation (first stray docstring).

 *  Can export (ugly but usable) module docs as Markdown, POD or
    manpage.

 *  Dropped useless features as --cat (one can always open the file)
    or display of partial documentation.

 *  Provided more rich usage hint.

 *  Rewrote tests with focus on more probable scenarios.

shellfu-get (whose only job is to print one of hardcoded strings depending
on $1) and shellfu.sh should be as light as possible.  Most of this code
is only useful (and intended) for library exploration, which is domain
of shellfu-doc.

A neat side-effect is, that in its new home, we don't have to be so
fussy about performance and footprinting, so we can afford luxury such
as putting code into functions and documenting them, using $1 for first
argument, using shellfu libraries(!)...

Needless to say, this is an incompatible CLI change (or it would have
half the effect), so we take the opportunity to re-do the CLI to match
the new home.

so that tfkit can now be tracked in separate repo.  (In future we might
add it as submodule)

Once simple.sh has been cleaned up and simplified in previous ~10
commits, it turns out that all it does is manage subtests.

Reflect that in the name.

(Doc will be updated later.)

Support test folder structure where test, oracle and generated result
data are stored each in separate directory.  This makes it easier to
ensure legible diff output without cluttering the filenames too much.

Most changes are in tf_do_subtest.

 *   Separated setup/cleanup logic from test data collecting and
     execution/evaluation.

 *   Revamped the execution/evaluation logic in a new tool testflt,
     allowing tester to use it as the need be.

 *   Code to compose actual test command removed, as testflt makes it
     easy to write the code in one place (TF_RUN) and keep simple things
     simple.

 *   Removed tf_parse_meta, as it's obsolered by above changes.

 *   Updated tests to reflect the new style.

This new hierarchy makes it easier to work simultaneously on data and
the script, simplifies deployment to tempdir and makes the launching
script naming consistent with simple.sh.