schemas/vegbien.sql: publish(), rm(): documented runtime (1 min)

schemas/vegbien.sql: added datasource_unpublish()

lib/sql_io.py: automatic handling of input/output column type mismatches: also do this for identifying columns, which first cause an error in a join in sql.distinct_table() rather than in the main insert (and thus were not handled by the existing error handling). previously, the user would have had to manually cast the input column in postprocess.sql. this involves getting handle_MissingCastException() to update join_cols as well as mapping.

lib/sql.py: distinct_table(): don't cache the table creation, because this prevents different distinct_tables from being created for the same input table

lib/sql.py: create_table(), copy_table_struct(): support custom query options, such as cacheable

lib/sql_io.py: put_table(): main loop MissingCastException handler: factored out into nested function so that it can also be used elsewhere

lib/sql.py: parse_exception(): parse "operator does not exist" errors as MissingCastExceptions (these appear when a staging table column is of the wrong type)

bugfix: /README.TXT: Full database import: Check that source contains [# datasources] rows up through XAL: added alternative verification method when this is not the case (some datasources may be near the end depending on import order)

schemas/vegbien.sql: public_validation: split into separate subschemas for plots, specimens, traits

schemas/Makefile: vegbien.sql: support auxiliary schemas besides *_validation