[xpath_functions] Implement distinct_values xpath function
On some websites, html content can be duplicated. This can be overcame but it can lead to complexe/fragile xpaths. distinct_values allow to solve this cases by unifiying duplicated values.
On some websites, html content can be duplicated. This can be overcame but it can lead to complexe/fragile xpaths. distinct_values allow to solve this cases by unifiying duplicated values.