schemas/vegbien.sql: Merged provider_view, provider_count, and owner_count into provider_count, using the combining query for Brad's data providers page at <http://bien.nceas.ucsb.edu/bien/people/data-providers/>

schemas/vegbien.sql: sync_taxon_trait_to_view(): Changed pkey to index because there can be multiple values of the same taxon's trait from different observations

mappings/Makefile: VegCore.csv: Filter out the VegCore tables so they are not matched as terms. This is necessary because some terms have the same name as a table, but the term should be the match rather than the table.

sql.py: DbConn.col_info(): raising sql_gen.NoUnderlyingTableException: Fixed bug where also need to catch DoesNotExistException, which is thrown by ::regclass

sql.py: DbConn.col_info(): Fixed bug where need to run run_query() recoverably, because this query throws an exception if the column's table does not exist (the information_schema query just returned no rows)

sql.py: DbConn.col_info(): Fixed bug where need to use pg_get_expr() on pg_attrdef.adbin instead of shortcut field adsrc, because adsrc does not include schema qualifiers on table names (including strings passed to `nextval('..._seq'::regclass)`)

sql.py: DbConn.col_info(): Fixed bug where need to pass through cacheable param to run_query()

sql.py: DbConn.col_info(): Fixed bug where need to use .to_str(self) instead of self.esc_value() because self.esc_value() expects a value, not a sql_gen.Literal instance

sql.py: DbConn.col_info(): Fixed bug where self needs to be used everywhere that db normally is, because this is a DbConn method rather than a global function

sql.py: DbConn.col_info(): For PostgreSQL, use pg_catalog tables directly instead of their views in information_schema. This allows using ::regclass to look up the table in the search_path, and fixes a bug in imports with an explicit public schema where column types were looked up in public instead of public.<version>. Also don't wrap default using sql_gen.as_Code() when it's None (indicating no default value, aka default=NULL), because this value is interpreted specially by sql_gen.TypedCol.