Data Grid: Define column separators used for copy/paste

Provide an option to define the character(s) used to separate columns in data copied from the grid.

Spaces are currently used for this which is next to useless as it makes it impossible to differentiate column boundaries from word boundaries in data values. If a fixed character is to be used, then it should be a tab (ASCII 0x09) as this unlikely to occur in database values and enables data to be pasted into spreadsheets as separate columns.