fix utils.py to not load contents as file paths

[JaeTLDR]

Looks like PyLode is attempting to open a file with ontology however if this is a serialised graph the server can error trying to load this file

I have added a small simple detection logic however it may be simpler to pass the ontology variable to RDFLib and get it to do the path vs graph and the file type detection rather than rolling its own. Additionally i noticed a lack of strip() on the imput, this may cause errors with the data type detection not firing corretly

[edmondchuc]

Thanks, I've refactored the code a bit and added a test.