Adds new webpack tree shaking plugin

Uses webpack for all of it

Changes rebase & reset terminal commands to apply to all commit nodes

Consolidates ui dependencies & build into main

Preserves spaces in format strings

Less roundtrips through to the UI on changes for better performance/UX
Also adds "flash" protection to deal with the active editor changing to undefined between changes

This setting allows disabling/enabling showing avatars in hovers. We
already have settings for the explorer and blame gutter, so it makes
sense to also have one for the hovers.

Closes #419 - Make blame heatmap color configurable

Closes #209 - Open File in Remote should ask for a branch if no upstream