New "dataFilterValue" and "dataNoFilter" options to allow filtering using "data-" HTML5 attributes

This one is a totally new feature (!) and has to be tested (I use it and it seems to work but I may have miss some cases ...).

The idea is to allow developers to choose what will be filtered defining a `data-XXX=YYY` attribute in a `td` element, which will be used to match the filtering string instead of the content of the `td`. Another `data-ZZZ` attribute can be defined to NOT filter a cell at all.
The rule is quite simple:
- if a `td` have the attribute defined, even with an empty value, this value is used instead of the `td` content
- if another `td` does not have the attribute, its content is used (like the original behavior).

Original commit message:
- adding the « dataFilterValue » and « dataNoFilter » options in js filtering
- new « filtertable-sample-data-filtering.html » example
- new options in the README for data options how-to

Notes:
- I added the word "modified" to the version number in JS files (for info)
- I made the minified version with an ugly online tool ...