schemas/vegbien.sql: specimenreplicate.institution_id: renamed to duplicate_institutions_sourcelist_id, as decided in the conference calls (wiki.vegpath.org/2014-03-13_conference_call#schema-changes-2)

fix: schemas/VegCore/mk_derived: added `EOF` at end to avoid (benign) "here-document delimited by end-of-file" warnings on Linux

fix: schemas/util.sql: trim(): by default, cascadingly drop dependent columns so that they don't prevent trim() from succeeding. note that this requires the dependent columns to then be manually re-created.

added schemas/VegCore.ERD.pdf symlink for easy access

bugfix: schemas/util.sql: is_constant(util.col_ref): updated to include standard newline at beginning of comment (applies to newly-imported staging tables)

*{.sh,run}: use new begin_target instead of `echo_func; set_make_vars`

fix: schemas/util.sql: explain2notice_msg(): don't include EXPLAIN output for simple, single-value queries, to avoid cluttering up the log output

schemas/util.sql: added fold_explain_msg()

bugfix: schemas/util.sql: set_col_types(): need to COALESCE the executed SQL to '' because util.eval() does not support NULL (and shouldn't, because this indicates a missing COALESCE in constructing the statement)

schemas/util.sql: set_col_types(): use simpler util.eval() instead of manual EXECUTE/util.debug_print_sql()