Fix all querystring keys starting with name specified will match

[nigrosimone]

This pr fix the issue where all querystring keys starting with name specified will match the accepted query strings.

If the user add the key foo, the rule all querystring keys starting with foo, eg.: foobar.

This happen because at line:

$val .= ( strpos( $val, '=' ) === false ? '.*?' : '' );

the rule become
foo.*?
instead of
foo=.*?

the simple fix is add a = into the rule, eg.:

$val .= ( strpos( $val, '=' ) === false ? '=.*?' : '' );

now, the rule become:
foo=.*?

Main PR is #380