Oskari 3.0 bundle lazy-loader

[ZakarFin]

Continues: #2791 and adds oskari-lazy-bundle loader that works with the new oskari-bundle loader.

Now we have both loaders with new versions for application main.js usage:

• oskari-bundle replaces oskari-loader and supports more streamlined bundle registrations
• oskari-lazy-bundle replaces oskari-lazy-loader for adding support to lazy-load bundles with the streamlined bundle registration

Moved some internal'ish functions around the core (from releasenotes):

These changes shouldn't really affect your app, but things that have changed inside the "engine":

• New core component src/BundleRegister for managing bundles and exposes Oskari.bundle() (previously part of src/loader.js) and Oskari.lazyBundle() functions.
• Oskari.bundle_manager functions removed:
  • registerDynamic() - replaced by BundleRegister.lazyBundle() that is exposed as Oskari.lazyBundle()
  • loadDynamic() - moved to src/loader.js as private function as it doesn't need to be exposed