Implement client side templates

[johnbillion]

See #291.

This begins the process of switching to client side Underscore templates while retaining the ability for any outputter to continue using server side HTML generation.

The first panel to be switched over to an Underscore template is the Admin Screen panel.

[shadyvb]

I think you should either add underscore or remove jquery, as wp-util depends on both.

[johnbillion]

I think I'll add Underscore so the dependencies are more explicit.

[tomjn]

Doing this via React or Vue might make more sense, QM can output the entire debug info to be displayed as JSON and it be passed down the hierarchy, the only things that need state being hiding one panel and showing another.

Also, using underscores templates brings with it the problem that content security policies can't remove unsafe eval etc on the frontend

[johnbillion]

I wanted to avoid loading another dependency that isn't included in WordPress, but you're right that React or Vue would be a better choice.

This is on hold at the moment anyway.

[lkraav]

I wanted to avoid loading another dependency that isn't included in WordPress, but you're right that React or Vue would be a better choice.

React will be shipping w/ Gutenberg soon enough. At least the dependency shipping problem looks solved.