Add validator for tagger

[awest25]

Work with @cj and @pavan to create a validator that highlights errors as you tag.

This will be a function that's called in the tagging page every time a row is added (saved). It will take as input the table data, active row, as well as the match metadata. It will return an array of taggingError objects.

Each taggingError object will have:

• Description: to assist the tagger in correcting the error
• An array of cells to highlight as an array of (row,column). (If either is null, highlight the whole column)
• An enum called severity (with maybe 3 levels). If it's severe, the form can't be submitted until it's corrected.

[awest25]

TODO:

• Deteting points is broken
• Highlight whole row very lightly red when there's an error anywhere