Add support for url constructor arguments in inline script tags

[jakemac53]

Currently, @HtmlImport doesn't work right if it appears in a separate package with a relative url inside of an inline script tag. The ScriptCompactor makes a new file next to the original entry point and doesn't know how to detect relative urls that it should fix up.

This could possibly be done with an @url annotation on the constructor field, or something along those lines.