refs #7494 make sure to apply disableCookies before any other method that could potentially set a cookie

It was modified twice today and got a merge conflict

 Previously was using unescape which did not work well with utf8 non ascii characters.

 refs #7231 refs https://github.com/piwik/piwik/commit/f5ed4fdc56fb0096ba18a9832a3f9fd8d48ed8b4

Fixes #7368 - Do not set user id when it's set to empty string or it would set the same visitor id to all those visitors

Refs #7290 - Set Visitor UUID not as a constructor parameter, but initialise it from first party cookies

Refs #7290 Fixing wrong logic in the JS tracker: make sure Visitor ID is initialised properly in all cases

location.href and top.document.referer are both already URL encoded.
To prevent double encoding we need to decode them.

fixes #7056 apply userId first before tracking anything to make sure userId is always set and does not randomly create new visits

refs #7043 do not cast a null value in userId to string as it would result in a string null, check whether it exists instead