Fixing bug caused by typo in core/Config.php (caused non-existant config sections to contain old superuser bridge info on first access).
Maintain accidental default behavior due to old typo bug (return empty array() when config section doesn't exist in INI config).
Added AJAX form directive for angularjs.
Merge pull request #6399 from piwik/angular_forms

Added angular directive that automates logic for AJAX forms.