Create dataset loader for Plant-Disease corpus

[davidkartchner]

Adding a Dataset

• Name: plant-disease
• Description: Dataset with tagged plant/disease entities, as well as relations on how the plants affect the tagged diseases
• Task: NER, RE
• Paper: A corpus of plant–disease relations in the biomedical domain - Data: http://gcancer.org/pdr/
• License: None
• Motivation: This is a robust benchmark for NER and RE models, as well as a useful resource for NLP-based identification of plants that can be used to treat diseases.

[davidkartchner]

#self-assign