Implement SVG path optimizations and add BezPath iterator

[joshi-07]

This commit addresses issues #18 and #29:

Issue #18 - Enhanced SVG path optimizations:

• Collapse repeated horizontal and vertical lines into single commands
• Convert degenerate quadratic and cubic curves to lines
• Drop leading zeros from decimal numbers (0.5 -> .5, -0.3 -> -.3)
• Existing optimizations (relative coords, smooth curves, nop removal) preserved

Issue #29 - Added PathWithPosIter:

• New iterator that tracks current position while iterating path elements
• Returns PathElWithPos containing element, current position, and subpath start
• Eliminates code duplication between Unchanged and Compact path styles
• Both path styles now use the shared iterator for position tracking

The changes maintain backward compatibility while adding the requested functionality.

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