don't allow to create a file or folder named 'Shared' in the root folder, also exclude all combinations of lower and upper case letters

Forward port of 762b0d9 from stable6 to master

269f24cf was not changed in setup.php which prevented loading of CSS files in some environments (e.g. my local setup) for apps.

This fixes alter table commands that didn't quote the old column name

This can be confusing and/or annoying

Forward port of 6d3b5b24fd4f82c1cbfbc4cade5246a0335f8dda to master

The "deleteAll" method on the Common storage class isn't used anywhere.
Also, it isn't defined on the Storage interface so this fix removes it
completely.

The method deleteAll() doesn't officially exist on the Storage class as
it's not defined on the interface, which means it fails on the Quota
storage wrapper and might fail on some external storage classes.
Also, this here is the only use case for that one method.

Jenkins somewhat complains that there are already sent headers.