Modlauncher support

[LeafHacker]

Is your feature request related to a problem? Please describe. Currently launchwrapper is hardcoded

Describe the solution you'd like allow an impact json to specify both launchwrapper tweakers and modlauncher classes.

An optional array for tweakers and each modlauncher interface should be fine.

If both tweakers and modlauncher class arrays are present the user could choose, or a default could be hinted at by a field in the json.

#10 could also add a property specifying if compatible optifines should use launchwrapper or modlauncher.