Miscellaneous client enhancements

This release includes enhancements to the zoom control:

• The zoom control to allows for independent horizontal and vertical scrolling. The coupling of the two axis is controlled by a button at the origin.
• The zoom scales have been flipped, with negative values indicating zooming out.
• Zooming in beyond one to one is now supported.
• Implemented fractional zooming.
• The control now includes an interactive minimap that shows the viewport in relation to the entire dataset. Users can drag the viewport representation to scroll the viewport, or click anywhere in the dataset to move the viewport there.

The notion of syncing viewports has been greatly enhanced. There is now a dedicated control that allows viewports to sync on

• scrolling
• zoom level
• channel being viewed
• path on the measure layer

The control allows for the specification of relative sync offsets among the viewports to better support viewing images that have a known relative coarse offset.

The path on the measure layer can now be closed. This is accomplished by clicking a button on the entry for the last node on the table in the path control. This will enable the server to compute statistics in the specified region some time in the near future.

What's Changed

• Synced with the new {pyre::viz} implementation by @aivazis in #37
• Expanded the capabilities of the zoom control by @aivazis in #41
• Synchronization enhancements by @aivazis in #42
• Add support for closed paths on the measure layer by @aivazis in #44

Full Changelog: v0.9.1...v0.9.2