Implement whitelist

[adamchol]

Implements proper whitelisting - before parsing anything.

[yeoleobun]

Good idea. If we don't need to update the whitelist at runtime, we should consider remove the Mutex and set the whitelist during initialization. If no whitelist is provided, we can default to an 'allow-all' white list.

[adamchol]

Do you mean like a second field or some enum for a static whitelist? I do need a dynamic whitelist modified at runtime, that's why I did it this way.

[yeoleobun]

If dynamic loading is required, this implementation is reasonable. Thanks for the context.