sql.py: run_query(): Parse "types cannot be matched" error as MissingCastException to type text

sql_io.py: put_table(): Creating the into table: Fixed bug where in_pkey and out_pkey names would collide if the output and input pkeys have the same name (as is the case for SALVIAS.projects). This entails changing out_pkey to new into_out_pkey wherever the into table's out_pkey is created or referenced.

sql_io.py: put_table(): Combining output and input pkeys in inserted order: Changed sql_gen.Table to sql_gen.Col when creating the column references (they have a similar effect, so using the wrong type did not cause any tests to fail)

README.TXT: Added steps before the import to `svn up` and update the schemas

README.TXT: Merged Backups > After a new import and Data import sections into one Data import section that contains the steps to perform and back up an import. Note that many `svn diff` lines result from a change in indentation.

sql_io.py: put_table(): Combining output and input pkeys in inserted order: Fixed bug where column references would be ambiguous if the output and input pkeys have the same name (as is the case for SALVIAS.projects)

schemas/functions.sql: Added _nullIf() overload where the type param has type text, to handle cases where row-based import auto-casts all args to text in response to a 'could not determine polymorphic type because input has type "unknown"' error

schemas/vegbien.sql: party: Removed party_datasource unique index because it was causing problems with column-based import (due to multiple unique indexes covering the same columns in different ways), and because it prevented creation of more than one party per organization

xml_func.py: _if(): Documented that it must be run to remove conditions that functions._if() can't handle

README.TXT: Datasource setup: Testing: Added step to test column-based import (by_col=1), because it is stricter about types than row-based import and sometimes fails when row-based import succeeds