Making the center column background less transparent

[#54784742] Changes the opacity from 0.7 (70%) to 0.85 (85%) as requested in: 

https://www.pivotaltracker.com/story/show/54784742
Gemfile: safe_yaml 0.9.4 was removed force➙ 0.9.5

see: https://github.com/dtao/safe_yaml/issues/43
Align the svg drawing area, svgcanvas, inside the svg editor workspace.

[#54482200]
remove image snapshot from svg edit dialog
Make sure input field containing svg annotation is updated before form submit