Heading resize

[davidfig]

• store headings in db
• read and store headings in local variables
• use heading sizes when drawing grid
• use heading sizes when drawing headers
• use heading sizes when placing and drawing cells
• click headings
• find cell when clicking and dragging
• draw cursor
• draw multiselect cursor
• cursor style changes to resize on hover
• UI resize headings
• hiding column labels when too small for width
• save resizing
• handle drawing array-based cells

[davidkircos]

Already merged into Development