The codebase is filled with includes that are unused, and which thus can be removed. At the same time, the files often do not include all headers that contain the definitions used in those files. This change uses clang-format and clang-tidy to clean up the includes, with minor manual intervention to ensure the code compiles on all platforms.
`Json::Value::isConvertibleTo` indicates that unsigned integers and
reals are convertible to string, but trying to do so (with
`Json::Value::asString`) throws an exception because its internal switch
is missing these cases. This change fills them in (and adds tests).
Acknowledgements:
Ripple thanks Guido Vranken for responsibly disclosing this issue.
Closes#2778
