bugfix: check before storing rc (may be necessary in -analysis_topup mode) and warn about consequences of redefining it.

API extension: store() now also returns how many actual store operations (as opposed to fetching of already stored ones) it has performed

Back to num_required_workers' meaning "how many extra workers we need to add to this analysis"; fixing a scheduling bug/oversensitivity to manual change of batch_size

free 'Start' from dealing with 'a_multiplier' by using an input_id_template in PipeConfig instead; renamed 'Start' to 'DigitFactory' to reflect that

A 3-analysis pipeline with almost exclusive use of #substitution#; mysql_conn() and mysql_dbname() modified to transform urls as well

A cleaner example of a two-analysis pipelines with better demonstration of #substitution# and only implicit $self->o() references

Protect generate_graph.pl in table-drawing mode from printing too many rows (by setting a limit in JSON config)

Protect generate_graph.pl in job-drawing mode from printing too many jobs (by setting a limit in JSON config)

cosmetic:  added new commits to README and renamed it Changelog; split out the old README.txt (non-Changelog part)

JobFactory uses $overriding_hash to create jobs/rows from input_id_template; 'input_id' parameter deprecated; standaloneJob supports templates.

Substitution machinery now supports an extra $overriding_hash that contains parameters with higher precedence than the whole of param() structure

fixed several problems with parameter substitution and detection of undefs; added param_required() and param_is_defined()