Remove Exception Class

[ldicker83]

Remove the Exception class and all references to it (see issue #13).

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From Issue #13

In an effort to reduce unnecessary code and to conform with modern C++ standards, the Exception class should be deprecated in favor of using exception classes derived from std::runtime_exception. This will provide a much cleaner interface, allows the rest of the library to throw specific exception types where applicable and set exception messages using a standard interface.

[ldicker83]

No point in maintaining the interface as nobody besides me atm is using NAS2D. Just go ahead and rip it out as it's been completely deprecated in favor of throwing specific exception types derived from std::runtime_error.

[ldicker83]

Complete as of e8e6a18