schemas/util.sql: added raise_undefined_column() for use in translating other exceptions to undefined_column

bin/map: map_table(): Resolve prefixes: combined db_xml.ColRef() constructor call with creation of args (as tuple) for clarity

bin/map: update_in_label(): use in_schema instead of the map spreadsheet column name when available, to allow using one spreadsheet for all datasources (which would not have a datasource-specific spreadsheet column name)

schemas/util.sql: added mk_source_col(), which uses the schema name instead of the map spreadsheet header to get the datasource name

schemas/util.sql: added table_schema()

added planning/goals/iPlant_BIEN_Proposal_Final.pdf with Mark's e-mail notes in iPlant_BIEN_Proposal_Final.pdf.notes.txt

bugfix: schemas/util.sql: mk_map_table(): add trigger to remove metadata value entries from the map spreadsheet as it's being imported, since these do not correspond to actual columns in the staging table and will produce an error when trying to rename nonexistent columns to them. note that these entries will still need to be included properly in VegBIEN.csv, which will require changes to the VegBIEN.csv make target.

empty inputs/*/import_order.txt: added subdirs in the order they are used by inputs/input.Makefile, by running make on the inputs to auto-populate import_order.txt. import_order.txt is needed by the runscripts to run the right set of subdirs in the right order.

added inputs/.TNRS/grants.sql, with statements to provide SELECT access to bien_read. these statements must be in grants.sql to avoid them being filtered out by pg_dump_limit.

inputs/input.Makefile: added support for separate grants.sql file, which may contain GRANT statements that would normally be filtered out by pg_dump_limit