[repository api] definitly kill usage of word 'pool' to refer to connections set used by a session
Also document session's data storage and some other internals.
Hopefuly things will get clearer.
Closes #1684860: vocabulary confusion in repository code: notion of 'pool'
\.svn
^build$
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\~$
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\.swp$
^doc/book/en/apidoc$
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.*/data/database/.*\.sqlite
.*/data/database/.*\.config
.*/data/database/tmpdb.*