Add support for lexemes

[Teester]

Lexemes currently get the "failed to validate schema" error message.

Support for lexemes needs to be added to the api. This required determining the important prefixes used by lexemes and translating them into properties, forms and senses in shape.py. The analysis in compareshape.py will presumably also have to take into account forms and senses.

The userscript may also need to be updated if the html element ids and classes are different to the ones that are used in entities.

An initial partial solution may be to ignore certain prefixes and only analyse properties (which the api can currently do) so there's at least partial support available.

[Teester]

Current Status:

• Basic support
• Support for statements
• Support for lexicalCategory
• Support for language
• Support for Forms
• Support for Senses

[fnielsen]

Interestingly, https://entityshape.toolforge.org/api?entityschema=E34&entity=Lexeme:L468580&language=da does not work ("An error has occurred while translating this schema") while https://entityshape.toolforge.org/api?entityschema=E34&entity=Lexeme:L117&language=da does work.