Not all reporters use a format that supports this, so TeamCity
and Automake reporters still do not report it. The console
reporter now reports it even on successful runs, where before
it only reported the rng seed in the header, which was showed
either for failed run, or for run with `-s`.

CLoses #2065

This ended up being a surprisingly large refactoring, motivated
by removing a `const_cast` from `Config`'s handling of reporter
streams, forced by previous commit.

This describes the actual intention much better.

This means that the CLI interface now uses the new key-value oriented
reporter spec, the common reporter base creates the colour implementation
based on the reporter-specific configuration, and it also stores the
custom configuration options for each reporter instance.

Closes #339 as it allows per-reporter forcing of ansi colour codes.

Test case hashing includes tags and class name

As the hasher involves more code now, it was split out into its own file
and it got its own set of tests.

Closes #2304

This includes always compiling the ANSI and None colour
implementations, as they don't need to touch any platform
specific APIs, and removing their respective compile-time
configuration options.

Because the Win32 colour implementation requires Win32-specific
APIs, it is still hidden behind a compile-time toggle,
`CATCH_CONFIG_COLOUR_WIN32` (renamed from `..._COLOUR_WINDOWS`).

The commandline options for colours were also changed. The
option now uses different name, and allows to select between
different implementations, rather than changing whether
the compiled-in colour implementation is used through
"yes/no/default" options.