Support implicit conversion for primitive types.

[fadulalla]

resolves #51

• This only deals with primitive types using the conversion table from microsoft. It does not fix issue BigInteger context functions not working #37 as BigInteger is not a primitive, nevertheless it does lay the ground work for it if someone wants to take it on.
• The implementation does not use the complex comparison defined by the csharp language specification in section "7.4.3.4 Better conversion from type" (online version). Instead, it uses a simplified approach where for every implicit conversion performed, memberFunctionScore is incremented by one. The function with the lowest score is chosen. (A score of 0 indicates a perfect match between supplied arguments and candidate function parameters.)
• I removed paramsMatchArguments because it is not required (and keeping it introduces a bug with this implementation).
• I am not too sure of this approach so all aspects of this PR are open to suggestions.

Thanks for the speedy review of the inheritance issue btw, hopefully it'll be a while before you see another PR from me! :)