Add PredicateMatcher that takes an arbitrary predicate functions

Also adds `Predicate` helper function to create `PredicateMatcher`.
Because of limitations in type inference it needs to be explicitly
typed, like so
`Predicate<std::string>([](std::string const& str) { ... })`.
It also takes an optional second argument for description of the
predicate.

It is possible to infer the argument with sufficient TMP, see
https://stackoverflow.com/questions/43560492/how-to-extract-lambdas-return-type-and-variadic-parameters-pack-back-from-gener/43561563#43561563
but I don't think that the magic is worth introducing ATM.

Closes #1236

CMakeLists.txt

@@ -152,6 +152,7 @@ set(INTERNAL_HEADERS
         ${HEADER_DIR}/internal/catch_list.h
         ${HEADER_DIR}/internal/catch_matchers.h
         ${HEADER_DIR}/internal/catch_matchers_floating.h
+        ${HEADER_DIR}/internal/catch_matchers_generic.hpp
         ${HEADER_DIR}/internal/catch_matchers_string.h
         ${HEADER_DIR}/internal/catch_matchers_vector.h
         ${HEADER_DIR}/internal/catch_message.h
@@ -221,6 +222,7 @@ set(IMPL_SOURCES
         ${HEADER_DIR}/internal/catch_leak_detector.cpp
         ${HEADER_DIR}/internal/catch_matchers.cpp
         ${HEADER_DIR}/internal/catch_matchers_floating.cpp
+        ${HEADER_DIR}/internal/catch_matchers_generic.cpp
         ${HEADER_DIR}/internal/catch_matchers_string.cpp
         ${HEADER_DIR}/internal/catch_message.cpp
         ${HEADER_DIR}/internal/catch_registry_hub.cpp