Re-add deleted error events.

Some changes to errors.

Remove IconManager from core.

Remove unused method.

Remove annotated IconManager provider.

Switch errors to use a Set.

Remove urlBuilder params.

From everywhere.

Kill FrameContainer.getIconManager.

Fix CoreErrorsDialogModel

Make PgoramErrorEvents synchronous.

Make the IconManager injectable using a global config.

I'm planning on removing scoped IconManagers - it's a lot of effort
to maintain them and pass them in everywhere (instead of injecting
them) for almost no gain. I don't think we've ever set a per-server
or per-channel icon, and I can't imagine why we'd want to.

Remove PluginMetaData.getManager().

This is horribly icky and wrong. The only place it's used is
PluginFilesHelper, which can easily be given its own manager.

Also fix annoying shaded import.

Add a separate ServiceManager implementation.

Add test for HighlightManager, fix issues.

Alternative highlights were never added because the maps were
optimised away; then the list occasionally ended up with null
entries as they were added concurrently.

Bump autovalue.

Add core error dialog.

Split up client build file.

Makes it a bit less messy, and easier to find the right bits.

Remove defunct getCredentials method from build script.

Use correct assert methods.

Add a CommandErrorEvent and format.

Remove unused methods.