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 way it makes much more sense from logically-const point of view, and also means that concrete implementations don't have to always have a `mutable` keyword on the stream member.
It has become completely vestigial, as it only ever passed-through the argument down to a different function, and being private member function, it didn't even introduce a useful compilation firewall.
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.
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.
This fixes an issue where reporter with default-output to stdout would think that it was given a stream _not_ backed by console, thus not using colour.
This will become useful when reworking colour support, because Win32 colour support requires checking whether the output is stdout, which is done through the `IStream` wrapper.