formatters: always show fail summary, use verbose for inline.

You shouldn't need to specify `--verbose` on the command line to
get a summary of failing and pending examples, show them all the
time by default.  The `--verbose` switch now enables additional
inline reporting, where that makes sense.
* specl/formatter/progress.lua (footer): Always show summaries.
* specl/formatter/report.lua (footer): LIkewise.
(expectations): Show additional inline pending and failing reports
in verbose mode.
* GNUmakefile (specl_verbose_0): With V=1 use report formatter in
verbose mode, otherwise default formatter.

Signed-off-by: Gary V. Vaughan <gary@gnu.org>
refactor: move color selection to specl/color.lua.

To provide a more uniform use of color between built in formatters,
factor out hard-coded colors and look them up by content type.
* specl/color (colormap): Tabulate names of some useful colors, and
return it, defaulting to underlining unknown color lookups.
* specl/formatters/progress.lua, specl/formatters/report.lua: Use
it.

Signed-off-by: Gary V. Vaughan <gary@gnu.org>