Added --use-colour option to give finer control over colourisation.

--force-colour is still present but deprecated (will remove in v2)

include/internal/catch_interfaces_config.h

@@ -37,6 +37,11 @@ namespace Catch {
         InLexicographicalOrder,
         InRandomOrder
     }; };
+    struct UseColour { enum YesOrNo {
+        Auto,
+        Yes,
+        No
+    }; };    
 
     class TestSpec;
 
@@ -56,7 +61,7 @@ namespace Catch {
         virtual TestSpec const& testSpec() const = 0;
         virtual RunTests::InWhatOrder runOrder() const = 0;
         virtual unsigned int rngSeed() const = 0;
-        virtual bool forceColour() const = 0;
+        virtual UseColour::YesOrNo useColour() const = 0;
     };
 }