vegbien_dest: Added option to override the prefix of the created vars

schemas/vegbien.sql.make: Fixed bug where data sources' schemas were also exported by exporting only the public schema. Note that this also removes the "CREATE OR REPLACE PROCEDURAL LANGUAGE plpgsql" statement, so that it doesn't have to be filtered out with `grep -v`.

input.Makefile: input.Makefile: Use `$(catSrcs)|` instead of $(withCatSrcs) where possible

sql.py: pkey(): Fixed bug where results were not being cached because the rows hadn't been explicitly fetched, by having DbConn.DbCursor.execute() fetch all rows if the rowcount is 0 and it's not an insert statement. DbConn.DbCursor: Made _is_insert an attribute rather than a method, which is set as soon as the query is known. Added consume_rows(). Moved Result retrieval section above Database connections because it's used by DbConn.

sql.py: pkey(): Fixed bug where queries were not being cached. Use select() instead of run_query() so that caching is automatically turned on and table names are automatically escaped.

streams.py: Added LineCountInputStream, which is faster than LineCountStream for input streams. Added InputStreamsOnlyException and raise it in all *InputStream classes' write() methods.

sql.py: DbConn: For non-cacheable queries, use a plain cursor() instead of a DbCursor to avoid the overhead of saving the result and wrapping the cursor

Moved db_config_names from bin/map to sql.py so it can be used by other scripts as well

csv2ddl: Also print a COPY FROM statement

input.Makefile: Fixed bug where input type was considered to be different things if both $(inputFiles) and $(dbExport) are non-empty. Now, $(inputFiles) takes precedence so that the presence of any input files will cause a DB dump to be ignored. This ensures that a (slower) input DB is not used over a (faster) flat file.