Revert "Enhance bridge for better target merging"

This reverts commit d3298324561a11e68f2690ee2863f8dbab17db2a.

Conflicts:
	h/static/scripts/plugin/bridge.coffee

Fix #1020
Remove dead code

The `highlights` stub is no longer needed in the sidebar because
with the new highlights plugins that @csillag made the sidebar no
longer has any code that accesses this property.
Remove unused target ignore

The guest frames should not be overwriting the targets when they
fail to anchor an annotation. Instead, the anchors property is
used now to store the realized anchors from the target data.
Track target blocks by $index

Removes the $$hashKey from the targets.

Ref #1207
Merge pull request #1500 from hypothesis/1020-bridge-races

Clean up unused code for bridge race conditions
Remove assumptions about .highlights and .target

Now there should be no code in the application that assumes the
existence of either of these.
Get quote for search from the TextQuoteSelector

Now when we track down where the quote property on the target is
coming from (#1207) our search will still work.
Quote search should match any quote selector
Update annotator to typed-packaging@ce90a27

Updates PDF plugin and stops creating excess quote properties.
Get quotes for excerpts from selectors

And remove the currently unused show differences things.
Update Annotator libs to typed-packaging@9e0eff3

Incorporates changes to the PDF plugin to support more recent PDF.js.
Move .webassets gitignore to top level
gitignore the generated Python MANIFEST file
Fix search on standalone pages

Using the searchbar will perform a stream search

Fix #1494