Support gesture events

[natmark]

Reopen #102
Fixed #80
Gesture model not to load ProcessingView. (Because ProcessingView is not a member of ProcessingKitCore)

[codecov]

Codecov Report

Merging #103 into master will decrease coverage by 0.91%.
The diff coverage is 68.65%.

@@            Coverage Diff             @@
##           master     #103      +/-   ##
==========================================
- Coverage    68.1%   67.19%   -0.92%     
==========================================
  Files          31       33       +2     
  Lines        1132     1198      +66     
==========================================
+ Hits          771      805      +34     
- Misses        361      393      +32

Impacted Files	Coverage Δ
ProcessingKit/Core/Context/Context.swift	100% <ø> (ø)	⬆️
ProcessingKit/Core/Extensions/CGPoint.swift	55.55% <0%> (-44.45%)	⬇️
ProcessingKit/Core/Shape/Shape.swift	95.61% <100%> (+0.11%)	⬆️
ProcessingKitTests/GestureTests.swift	100% <100%> (ø)
ProcessingKitTests/ShapeTests.swift	98.66% <100%> (-0.16%)	⬇️
ProcessingKitTests/Extensions/CGPath.swift	100% <100%> (ø)
ProcessingKit/Core/Input/Gesture.swift	36.2% <36.2%> (ø)
...t/ProcessingView+Core/ProcessingView+Gesture.swift	38.46% <38.46%> (ø)
ProcessingKit/ProcessingView.swift	78.34% <72.46%> (+0.19%)	⬆️
ProcessingKitTests/Extensions/CGPathElement.swift	73.33% <73.33%> (ø)
... and 9 more

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