README.TXT: Datasource setup: Add input data for each table present in the datasource: Don't add a CSV or create.sql file for tables that are in a .sql export

README.TXT: Schema changes: Sync ERD with vegbien.sql schema: Changed instructions to just select tables with arrows next to them rather than all tables, because each table that's updated will have its lines reset and the number of lines that need to be fixed should be minimized

README.TXT: Datasource setup: Accept the test cases: `make inputs/<datasrc>/test by_col=1`: Clarified that errors could indicate bugs in the VegBIEN unique constraints

README.TXT: Data import: To remake analytical DB: Added explicit public schema setting since the analytical DB is often manually remade after the public schema has been renamed. Removed warnings that certain commands must be run after running make_analytical_db, because the "remake analytical DB" instructions no longer require this.

README.TXT: Datasource setup: MySQL inputs: Added steps to export the database to a PostgreSQL-compatible .sql file, which can be directly used by the install process without the need to export each table as CSV

README.TXT: Datasource setup: Choosing a table name: Documented that for .sql exports, you must use the name of the table in the DB export, not a suggested or custom name

input.Makefile: Staging tables installation: $(dbExports): Also include the files that would be generated by running _MySQL/*.make and creating the corresponding PostgreSQL translations

input.Makefile: Staging tables installation: Moved .sql export downloading and translation to separate Input data retrieval section

Added lib/MySQL.{data,schema}.sql.make templates to use in datasources' _MySQL/ dirs

inputs/import.stats.xls: Updated import times