This ensures that the arc shapes remain correct after removing
a point belonging to an arc or inserting a point in the middle
of an arc.
Simplify implementation of Replace( ..., aP ). Now a Remove
operation followed by an Insert operation.
Improve QA test for SHAPE_LINE_CHAIN Append, Insert and Replace
Implement SHAPE_LINE_CHAIN::splitArc to break up an arc into two
Implement SHAPE_ARC::ConstructFromStartEndCenter and add qa test
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