syntax highligting, move unit tests for abap to abap class, xml to xml class
this avoids having cyclic references, previously HIGHLIGTER called FACTORY which instantiated ABAP which inherited from HIGHLIGTER
* add minimal unit test
* readd new keywords to abap syntax highlighter
- removed duplicates from keywords
- removed deprecated pseudo comment
- explicitly remove duplicates from keywords to avoid needless dumps
Co-authored-by: Lars Hvam <larshp@hotmail.com>