Merge remote-tracking branch 'origin/fastpath'

* origin/fastpath:
  Improve documentation
  Fix the btest "-c" option
btest now sets a new environment variable TEST_VERBOSE.

   ``TEST_VERBOSE``
       The path of a file where the test can record further
       information about its execution that will be included with
       btest's ``--verbose`` output. This is for further tracking the
       execution of commands and should generally generate output that
       follows a line-based structure.
Adding a new "alternative" concept that combines filters and
substitutions, and adds per-alternative environment variables.

Instead of defining filters and substitutions separately, one now
specifies an alternative configuration to run with "-A <name>" and
that then checks for both "[substitutions-<name>]" and
"[filter-<name>]" section. In addition, "[environment-<name>]" allows
to define alternative-specific environment variables.

The old filter/substitutions options -F and -s are gone. The sections
for substitutions are renamed to "[substitutions-<name>]" from
"[subst-<name>]".
Updating CHANGES and VERSION.
Allowing use of -j without value.

BTest then uses multiprocessing.cpu_count()
Fixing links in README and removing TODOs.
Fix for alternative names containing white spaces.
New @TEST-ALTERNATIVE that activates tests only for the given
alternative.

Also renamed @TEST-NO-ALTERNATIVE to @TEST-NOT-ALTERNATIVE.

Also allowing "default" for both @TEST-ALTERNATIVE and
@TEST-NOTALTERNATIVE to specify the case that BTest runs without any
alternative given.
Bugfix for -j without number.
s/bro-ids.org/bro.org/g
Adding Sphinx sandbox for testing.
Fix for tests returning no output to render at all.
Restructuring the btest directive.

We now process it in two passes: one to save the test at parse time,
and one later to execute once everything has been parsed. No
functionality change, this will later enable defining tests in
multiple parts.
Default configuration file can be overriden via BTEST_CFG environment
variable.
Adding CommandPrefix option.

CommandPrefix
    Changes the naming of all btest commands by replacing the
    "@TEST-" prefix with a custom string. For example, with
    "CommandPrefix=$TEST-", the @TEST-EXEC command now becomes
    "$TEST-EXEC".
Adding Initializer option, which runs a command before each test.
Documentation updates.
Smaller fixes and tweaks.

Includes:
    - When creating directories, we know also create intermediaries.
      That in particular means that "@TEST-START-FILE a/b/c" now
      creates a directory "a/b" automatically and puts the file in
      there.

    - IgnoreDirs now also works for sub directories.
A test-suite for btest. Using, of course, btest.

"make test" will test most of btest's features. The main missing piece
is testing the Sphinx support, we will add that next.
Portability fixes for test suite.