Check file size limit in HTML editor

The HTML editor does not open files that are too big to prevent excessive memory usage. The limit is configured using the folder.editFileSizeLimitBytes property.

When the HTML editor opens a file, the file size limit is checked. If the limit is exceeded, opening the file is rejected. The problem is however, that when creating the file the limit is not checked at all. This leaves the user in the dark, creating of too large files is possible but later editing of those files not.

The solution is to check against file size when saving as well. An error should appear.

In addition, the default limit should be raised to 2MB.