Remove URL from PluginManager

[dakrone]

We should be using URI instead.

It'd be great to eventually get new URL(...) in the forbidden APIs also.

[rjernst]

+1

[rjernst]

The plugin manager was completely rewritten since creating this issue. It still uses new URL, but only in the case that a URL is passed in (in which case the plugin id is not a builtin plugin or a maven identifier). We need URL because we need to open a connection; URI only has information about the URI, but you still need to call toURL() to get something that can open a connection.

[dakrone]

+1, thanks for closing this Ryan