Add import checks

Ingestion is currently a largely manually and therefore error-prone process. It would be very helpful to have scripts that checked for various common problems. Some of these could include:

- Extract the title from a PDF and ensure it lines up with the metadata in order to avoid [problems like this one](https://github.com/acl-org/acl-anthology/issues/128).
- Look for instances of missing LaTeX-protected capitalization
- Ensure the abstract is present
- Look for LaTeX artifacts
- Look for PDF cut-and-paste artifacts in the abstract (e.g., hyphenation)
- Look for names that are all lowercase (usually a mistake)
- (Many others)

Start by reviewing the ingestion process and the list of proposed checks in the issue. Determine which checks are in scope and how their findings should be reported; done means the agreed checks run reliably and catch the listed metadata, LaTeX, abstract, and PDF text problems.

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