Made Clara a “Cliche” header, which will be usable independently of Catch.

- This is just a first step. It still has a dependency on catch_text.h, which also needs to be made a Cliche header.
- These then need their own homes on GitHub.

projects/SelfTest/TestMain.cpp

@@ -16,7 +16,7 @@
 
 template<size_t size>
 void parseIntoConfig( const char * (&argv)[size], Catch::ConfigData& config ) {
-    Clara::CommandLine<Catch::ConfigData> parser = Catch::makeCommandLineParser();
+    Catch::Clara::CommandLine<Catch::ConfigData> parser = Catch::makeCommandLineParser();
     parser.parseInto( size, argv, config );
 }