Rework DOM updates, to direct JS calls

[dignifiedquire]

Original Motivation: Make it easier to implement Dom Refs. Follow on Motivation: Less Javascript in your source files ;)

In light of https://github.com/fitzgen/dodrio/issues/77#issuecomment-492733762 I reworked the way DOM updates are sent. Instead of copying the changes in an OP list to JS land, this calls bindings through web-sys directly.

Perf:

As far as I have measured very similar to master. Tested both current Firefox and Chrome.

Non scientific screenshots of running the triangle example

master

x-direct

Missing:

• 1 test is failing, could use some pointers as to why. For some reason the new version adds the event attributes, but they are not expected to be there in the js test
• some small TODOs on setting attributes
• more testing?