* Session::applyCommandLine overload on wchar_t

This allows users on Windows to use Catch::Session::applyCommandLine
with wchar_t * arguments of application.

With this change Session::run became templated so both char and wchar_t
version have the same implementation.

This means

* Adding new configuration toggle `CATCH_CONFIG_DISABLE_EXCEPTIONS`
and a best-guess configuration auto-checking for it.
* Adding new set of internal macros, `CATCH_TRY`, `CATCH_CATCH_ALL`
and `CATCH_CATCH_ANON` that can be used in place of regular `try`,
`catch(...)` and `catch(T const&)` respectively, while disappearing
when `CATCH_CONFIG_DISABLE_EXCEPTIONS` is enabled.
* Replacing all uses of `throw` with calls to `Catch::throw_exception`
customization point.
* Providing a default implementation for the above customization point
when `CATCH_CONFIG_DISABLE_EXCEPTIONS` is set.
* Letting users override this implementation with their own.
* Some minor changes and ifdefs all around to support the above

Catch2's documentation promises that listeners are called _before_
reporters, but because of the previous implementation, they were
called _after_ reporters. This commit fixes that.

Closes #1234

Fixes #1215

The support is turned on by default but the user might need to be able
to turn it off which is now possible by defining CATCH_CONFIG_NO_WCHAR.

Needed to embed newer version of Clara

Closes #1178
Closes #1031

To prevent bugs with stitching system headers inside Catch,
the proxy header is responsible for guarding against inclusion
on Linux, rather than the includers.

Might be related to #1197