Add skeletal poppler backend
render_annotated_pdf_page function which uses poppler to write out SVG files with basic annotations (shapes) added
Specify png and svg filenames and connect to dump script.
Renamed render.py to diagnostics.py and added make_annotations() which describes how to draw the result of page_to_tables
Factored some code into a function
Started work on automatically rendering across all PDFs
Resolved pdf_filename vs pdfpath in dump.py
Fixed drawing rectangles, implemented drawing lines.
Minor, remove print
Renamed Annotation to AnnotationGroup