OpenMVG v1.6 "Halibut" is out

What's new:

• 24 PR has been handled.
• 22 issues/features enhancement has been completed.

OpenMVG core:

Graphics

• Add a helper class to manage to draw colors from gradient & heat bar/map #1594
• Add opacity support in svgStyle #1697

Multiview

• Add 3 two-view triangulation routines [1,2] Thx to @rjanvier #1623 #1645
• Add Upright Essential matrix solver [3] #1718
• Add relative upright up2p solver [4] Thx to @vlarsson #1721

Matching

• Add HNSWL2 matcher [5] @rjanvier #1665

Software/SfM

• Add ability to chose Triangulation and Resection/Pose method from command line #1729
• Add display of view-graph statistics in ComputeMatches #1662
• ExportToOpenMVS supports now grayscale images @junlinp #1709
• FrustrumExport top face is now colored @csparker247 #1702

Build enhancement