Initial support for MVA operators

This add 4 new operators to perform basic comparison with multivalued attributes

```
* |== At least one attribute should equal the value
* &== All attributes should equal the value
* |=~ At least one attribute should match the regular expression
* &=~ All attributes should match the regular expression
```

The allowed syntax are
```
attribute-name &==/|== "double quoted string with xlat expansion"
attribute-name &==/|== 'single quoted string for a fixed value'
attribute-name &=~/|=~ /regular expression/flag
```

With the regexp, we're not matching against group. It will not populate the ```%{0} %{1}``` variables

Their inverse is not available. Simply encapsulate their call inside ```!()```