Visual Studio integration part 1 - allow catch_message.hpp to be included by more than 1 source file

As discussed with Phil by email.

The counter for MessageInfo is now templated - this forces the compiler/linker to use greedy instantiation (or whatever process it needs to use) to remove duplicates of the static from the executable.

Also tidied up the VS2010 TestCatch project and delele the SelfTest executable in 'make clean' on *nix.

Tested on Windows (VS2010 & MingW) and Ubuntu 12.10.  Self tests all pass.

single include has *not* been regenerated.