Registration fields in CSV export and minor bugfixes/improvements

[FEATURE] Added isRequiredFieldViewHelper for required fields #550
[FEATURE] Added Validation.ErrorClass viewHelper #552
[FEATURE] Include registration fields in CSV export #524
[FEATURE] Enable iCal attachment for event in confirmation email #154
[TASK] Allow registration fields and field values on standard pages #563
[TASK] Refactor fluidStandaloneService #558
[TASK] Enable "exclude" option for all fields #553
[TASK] switch latitude and longitude field for better usability #551
[TASK] Fixed image rendering für documentation #530