Improve exception strategy

[barnabycolby]

Currently, almost all of the exceptions used are checked exceptions, meaning that if an exception is thrown, the caller is forced to handle it before the code will successfully compile. This regularly results in a large list of exceptions that callers must handle, some of which should never occur, unless as a result of programmer error. This leads to developer frustration and lazy exception handling, lowering the overall code quality. It would be far better to throw unchecked exceptions in these situations. Some thought should also be given as to whether the caller can actually do anything to recover from the exception. In some cases, recovery is impossible and therefore the code should throw a runtime exception. At the highest possible level in the code, a try catch clause should be added to handle these unchecked exceptions, and display friendly error message to the user.