Module renames

[daradib]

Renames some modules and classes.

• Renames DataLoader to TableLoader and moves it along with the database functions under an io module.
• Moves untested/unmaintained loading functions and rastertoolz under deprecated module, which is excluded from coverage.
• Requires that SRID be specified as an argument to the conform_srids function.
• Removes unused code for falling back to default SRID when loading shapefiles.
• Adds module docstrings.
• Renames Data Exploration to Data Extraction.