Support for ellipses
Refactored `draw-string`.

+ Support for string to shape.
Preliminary support for linear equation solving
First working version of the linear solver
Fixed some tests
Use maximum-absolute value to choose pivot
Fixed Gauss solver
Fixed inconsistent/unsolvable equations detection
Removed extra `println`
Preliminary support for constraint based geometry
Basic support for parsing infix expressions
Fixed infix parser
Fixed bug with parsing quoted infix sequences
Support for infix constraints on rectangular shape
Experimental support for shape groups
Support for rect coordinate extraction
Refactored `fold*`
Support for solving constraints on shapes
Force constant term in parsed infix equation
New map-based equation solver