Add option to disable generating System.loadLibrary()

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This is a draft because there should be more robust checks/parsing for the options.

Close #5

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Seems like I can't test the changes without publishing the windowsapi-code-generator with changes

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I figured out how to run this plugin without publicly publishing it -- publishing to the local maven repository.

And I have confirmed this change did help with my problem, but I think the better solution is to generate System.load() with absolute paths by default.