Fixing the issue of striping attributes when beautify

[BanulaKumarage]

• As mentioned in #398 attributes of the tag were missed when changing the tag from license to exception and beautify in the XML editor.
• It was fixed by updating the ATTRS_SEQ list in formatlXml.py by adding exception with its allowed attributes.
• In the Exception schema, standardLicenseHeader tag is not allowed. Therefore it is removed when submitting an exception.

[BanulaKumarage]

@jlovejoy Can you review this?

[jlovejoy]

@rtgdk - I'm not sure how the functionality for the "beautify" option works or if this is all that is needed to fix this issue. Can you please review??

[goneall]

@BanulaKumarage @rtgdk - Should this be merged?