[multi-sources-removal] Simplify ConnectionsSet internal structures and public methods
since it now handles a connection to the system source only
Related to #2919300
[jcr: adjust 3.17.11 migration, fix a number of bugs in new
ConnectionsSet implementation, fix
source.{open,close}_source_connections]
\.svn
^build$
^dist$
\.pyc$
\.pyo$
\.bak$
\.old$
\~$
\#.*?\#$
\.swp$
^doc/book/en/apidoc$
\.old$
syntax: regexp
.*/data/database/.*\.sqlite
.*/data/database/.*\.config
.*/data/database/tmpdb.*
.*/data/ldapdb/.*
^doc/html/
^doc/doctrees/
^doc/book/en/devweb/js_api/