CORE-3855 Refresh data panel after simple upload.
CORE-3753 Fixed validation in simple upload and URL import form.

Refactored the isValidFilename method into a isValidUploadField method that checks the upload TextField's validation in addition to checking for an empty filename.
Removed the logic to disable invalid upload/URL fields, since disabled fields always validate and those field values are now submitted separately rather than all at once by a parent form.
CORE-3753 Fixes for simple upload validation.

Removed the validateForm call from the FileUploadField Valid and Invalid listeners (the Invalid listener was causing a stack-overflow).
Added validateForm calls to the FileUploadField OnChange listener and the Reset button listener.
Updated the FileUploadField OnChange listener to specifically remove the "C:\fakepath\" string that Chrome adds to filenames in this field, since an invalid filename may contain invalid characters followed by a "/" or "\" that would all be removed, then the filename could pass validation after it was changed.
Removed extra filename.replaceAll calls, since these filename characters would already be removed by the OnChange listener.