[Maps] Add a Measure tool to Maps

[kmartastic]

As a consumer, I want to be able to measure the distances on a map. Considered a table-stakes feature for many mapping customers -- useful during ad hoc analysis or as a tool for an end-user to understand proximity.

Requirements:

• As a consumer, I want to be able to measure the distances between 2 or more points on a map.
• As a consumer, I want to be able to choose the units of measurement between Imperial and Metric and (feet or miles, metres or kilometres)
• Measurements are geodesic. Straight lines are local scales, and curved lines at global scales.
• As an author, I can disable the tool, so it is not available when added to a dashboard, etc.

UX:

• Enable the tool (the map is now in measure mode) - single-click to get started - single-click to add a vertex - double-click to finish the measurement.
• The distance should be displayed while measuring and update dynamically.
• After finishing a measurement the line (polyline) and measurement should remain in the view until a new tool is chosen, new measurement initiated, state of the map is changed.

Accessibility:

• User should be able to right-click and choose add-vertex or finish measurement.
• User should be able to use a keyboard shortcut to add-vertex or finish measurement.

[elasticmachine]

Pinging @elastic/kibana-gis (Team:Geo)

[elasticmachine]

Pinging @elastic/kibana-presentation (Team:Presentation)

[ThomThomson]

Closing this and adding it to our icebox.