- Added new exception class IllegalStateException
- Canvas class defineShape and defineTransparentShape now throw an IllegalStateException if the Canvas has not yet had anything drawn on it (eg. isClear() is true).
- Updates to com.flagstone.transform.util.shape.Canvas
    - Store current integer twips coords (intCurrentX, intCurrentY) for re-use later when computing deltas, etc.
    - Tweaks to _addLineRecords() to help reduce round-off issues with large quantities of relative lines
    - Tweaks to rcurve() to help reduce round-off issues when calculating deltas for control and anchor points