Resolve "Update record mapper to handle reference curve ID"

Closes #19 (closed)

• Reference to ref_curve_id in Configuration have been removed.
• Record mapper now takes the mnemonic of the first curve (or "" if no curves exist) directly from the LAS file and uses that as the ref_curve_id.
• Test updated to account for this change.

Note: I have also manually tested this with the bulk upload functionality and it works as expected.