[WIP] Add UI element for alternate resolution strategies like "Keep Both"

[al-the-x]

The plugin supports resolution via "Keep Both" methods acceptOursThenTheirs() and acceptTheirsThenOurs() but those options are "hidden" underneath the contextual menu (well, I certainly never thought to right-click on the conflict). Provide a UI element -- like a gear button? -- that will supply other resolution options.

• Original issue: #185
• See UI elements in SideView:
• See resolution fns in ConflictedEditor

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This change is

[al-the-x]

FYI, this is just a TODO in the code so I don't forget about it. Care to assign to me, @smashwilson?

[al-the-x]

@smashwilson See notes on my recent commits. Some insight would be helpful, if you have the bandwidth.

[ardean]

any news?