Resolve "Parsing tabular in the root level"

Closes #1456 (closed)

Reworking the tabular parser to have a better visual in both GUI and performance on the python side:

• Allow each data_file quantity to populate multiple (sub)sections in column, row or entry mode separately,
• Allow parsing the quantities in the root level of the TableData
• Remove the "root" mode. No longer necessary,
• Unnecessary inheritance of the TableData class in the sub_sections under mixed mode,
• Remove target_sub_section annotation,
• Add the option to the entry mode to allow creating new entries out of individual (sub)sections,
• Add a ReferenceEditQuantity field in the root level of the TableData to reference the freshly created entry