csv2ddl: Renamed schema name env var from datasrc to schema to reflect what it is, and to make the script general beyond importing inputs

input.Makefile: Moved Installation, Staging tables after Existing maps discovery because they depend on it. Staging tables: Create a staging table for each table a map spreadsheet is available for. Put double quotes around the schema name so its case is preserved.

Added csv2ddl to make a PostgreSQL CREATE TABLE statement from a CSV header

sql.py: Input validation: Moved section after Database connections because some of its functions require a connection. Added esc_name_by_module() and esc_name_by_engine(), and use esc_name_by_module() in esc_name().

input.Makefile: Installation: Create a schema for the datasource in VegBIEN as part of the installation process. This will be used to hold staging tables.

input.Makefile: Changed install, uninstall to depend on src/install, src/uninstall targets, which in turn depend on db, rm_db. This will allow us to add additional install actions for all input types.

sql.py: DbConn: Cache the constructed CacheCursor itself, rather than the dict that's used to create it

sql.py: pkey(): Changed to use the connection-wide caching mechanism rather than its own custom cache. DbConn.__getstate__(): Don't pickle the debug callback.

sql.py: DbConn: Added is_cached(). run_query(): Use new DbConn.is_cached() to avoid creating a savepoint if the query is cached.

sql.py: DbConn: Also cache cursor.description