Add parameters to getJavascriptTag API call

This pull request brings the getJavascriptTag API call up to parity with the Piwik Administrative interface (Tracking Code section) by adding three boolean parameters:

 - mergeSubdomains:  Track visitors across all subdomains of <site name>
 - prependDomain:  Prepend the site domain to the page title when tracking
 - hideAlias:  In the "Outlinks" report, hide clicks to known alias URLs of <site name>

Please note that the new code makes database calls.  I'm not certain how you normally sanitize user input so I have applied `Common::sanitizeInputValue()` to the variables that could be used to inject SQL.  Please provide guidance if you prefer a different strategy.