[tools/pdf] factorize get_pdf_rows into new class PDFTableExtractor
requested to merge bhm-heddy/woob:factorize_get_pdf_rows_into_new_class_PDFTableExtractor into master
To handle more pdf files, the get_pdf_rows method and all related methods have been updated to be part of a single class inside a pdf_table file. The purpose is to make it easy to overwrite these methods to parse different format arrays in new pdf.