UI: Add 'persistent controls' creation methods that link to prefs

[runegan]

Original report by Zack Lovatt (Bitbucket: zlovatt, GitHub: zlovatt).

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.addPersistentCheckbox("checkbox text", "prefsKey", onClick, properties)
.addPersistentEditText("default text", "prefsKey", onClick, properties)

So that they'll check the pref on load and update to reflect it, and then after being clicked they'll set the pref and then trigger the rest of the onclick