Replace lodash template in field formatters

[legrego]

Both the source and color field formatters rely on the lodash template function in order to generate their markup.

This function requires dynamic code execution, which prevents us from enabling a more restrictive content-security-policy. The field formatters should be updated to use another method of HTML generation, such as ReactDOMServer. renderToStaticMarkup(), which is designed to be used both client-side and server-side (despite its name)

[elasticmachine]

Pinging @elastic/kibana-app-services (Team:AppServices)

[mattkime]

@legrego are there any release goals for the improved CSP?

[legrego]

@mattkime nothing concrete at this point, but it's getting increased interest from the community