v1.7 start modify CssTable LayoutEngine
modify code
modify more
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rename CssLayoutEngineTable to CssTableLayoutEngine
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MAX_COL_AT_THIS_VERSION
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prepare CssTableLayoutEngine.TableColumn
1909: use TableColumn to hold column info

Modify CssTableLayoutEngine
1. use TableColumn to hold column info
2. remove naked float array (eg. _columnWidths , _columnMinWidths)
3. remove IsNan() usage in CssTableLayoutEngine class
Merge branch 'v1.7'