Dataset checks I

[tylerganter]

Adding functionality to validate labels and datasets for common issues that can be automated away. This functionality includes:

• ensuring the data filename is stored in the labels file
• fixing underscores versus spaces and conforming capitalization to a provided schema (syntax checker)

Start with dataset level functions, which have been added to eta/core/datasets/standardize.py

Then refer to eta/core/image.py and eta/core/video.py for support at the labels level (only for syntax checker)