Features pertaining to serial attribute-value pairs.

[KartikChugh]

• numAttrValPairs: the number of attribute-value pairs the element has.
  Regular: attribute, value completion
  Parent: tag, attribute, value completion

• prevAttribute: the attribute preceding the attribute-value pair extracted for the table

• prevValue

• prevAttrVal

• attrIndex: the order in which the attribute extracted for the table appears in the element

• valIndex

• attrValIndex