Also, stop passing ignored "spec" parameter.

Drop overly descriptive comments.
Simplify code.
Fix coding style.

Backward compatibility was not implemented everywhere, and it is masking
bugs: not all parameters were provided to these ZSQLMethods, which can
cause all sorts of bugs and performance issues because of DTML defaulting
to acquisition context for missing arguments. Drop this overcomplex code.

erp5_ingestion_mysql_innodb_catalog: index url_string in portal_type: Fax, Telephone, Web Page, Web Style, Web Script

by adding Base_downloadWithCors that acts like Base_download but
adds CORS headers according to Base_prepareCorsResponse.

By using Event_generateReference from erp5_crm

/reviewed-on !214

Allows accessing any catalog column after parent relation, instead of only
pre-configured columns.
Allows reverse relation lookup (for the non-parent part of the relation,
as child relationship is not supported).
Also, drop now-redundant related keys.

Simplifies extension.
Also, factorise constants a bit.

Change autocomplete from Ctrl-Space to Alt-Space, because
the former is already used for switching keyboard language.

Change indent less from Ctrl-] to Shift-Tab, because the
former is already used for switching between browser tabs.

@nexedi any objections ?

/reviewed-on !213

Including all external method arguments in the error is needlessly
verbose.
If you rely on this to debug, define this inside your external method.

Otherwise, longer results would be truncated and shorter results would
produce activities with an empty list as argument.