Teardrop v2

[KjellMorgenstern]

The PR replaces the original teardrop.

This is a proposal for discussion, since it breaks the original parameters. Not backward compatible, so probably not acceptable. I would be interested to improve it based on feedback, or push it as a "teardrop2" module.

How and why?

• Keep parameter names compatible with cylinder().
• 'angle' parameter to specify the height was not intuitive, as it rotated the whole cylinder, and maxed at 45 degree (angle=90 resulted in a 45 dregee slope. Steeper slopes, eg 60 degree were not possible)
• Added r1,r2 parameters, so teardrop cones can be created
• Added a bridged version (this was recently also added in the original teardrop)
• Better readable code. That might be a matter of taste
• Orientation of teardrop is same as the orientation of circles, use the ususal rotate method to align.

Code explained: The teardrop is constructed in 2D as the hull of a circle and a dot above the circle. This is then extruded to 3D. The dot is placed in the exact distance that is needed to reach a desired slope. For example, if you can print 30 degree overhangs, min_a = 30 results in a teardrop that uses a flat slope of 30 degree.

[rockstorm101]

For the reasons described in issue #32 this kind of API-breaking change would have to go into dev and not into master. And for the same reasons might require renaming some of the modules. Otherwise the changes look reasonable.

[KjellMorgenstern]

Thanks for the hint, I'll review this against dev branch