Add handling of additional characteristicNames that are the same constituent

[jbousquin]

Some variables have different names but represent the same constituent (e.g., "Total Phosphorus, mixed forms" and "Phosphorus"). Add characteristicNames that can be converted in the same way as an existing. May require:

• re-structuring of domains.out_col_lookup()
• filtering of results to limit qualifiers to those that are the same
• further development of domains.accepted_methods()

[jbousquin]

TADA SubstituteDeprecatedChars leverages https://cdx.epa.gov/wqx/download/DomainValues/Characteristic.CSV, replace 'Name' with 'Comparable Name' col based on 'Domain Value Status' == 'Deprecated'. 'Group Name' may help further categorize Accepted names.

[jbousquin]

Link to TADA docs in docs for table for this.