Modelines: add byte-order-mark & small fixes

Summary:
Changes:

• Add missing keyword: byte-order-mark (there is only "byte-order-marker" and "bom"). Obtained from: https://docs.kde.org/stable5/en/applications/katepart/config-variables.html
• Remove keywords delimiters "*" and "+", because in the "RemoveSpacesOptions" list, the keywords "*" and "+" are not highlighted.
• Fix ";" in the "RemoveSpaces" context ("remove-trailing-spaces" variable). The character ";" it is not highlighted as in the rest of the variables, since when writing a value, the context ends.

• For a strange reason, the use of <IncludeRules context="##Modelines"/>, in others files, causes the line continuation character ("\") to be highlighted as dsNormal. This is solved by removing the LineContinue rule in the "Normal" context in Modelines. I consider the LineContinue & DetectSpaces rules to be unnecessary in the "Normal" context, so I've eliminated them.

I was going to add a test file, but there are errors when generating the html and ref files, even with the unmodified modelines.xml file :S

Reviewers: turbov, dhaumann, cullmann, vkrause, Kate

Reviewed By: cullmann, Kate

Subscribers: kwrite-devel, kde-frameworks-devel

Tags: Kate, Frameworks

Differential Revision: https://phabricator.kde.org/D14274