response/backend cache short duration tune

[msaf1980]

• Change long cache duration to 3 hours and 2 minute until offset by default, also make until offset tunable.
• Recalc duration on from/until timestamps truncate.

[Civil]

It would be great to have a few lines somewhere in the docs about what is ShortTimeout and ShortDuration, as names of the options are not self-explanatory.

[msaf1980]

Documentation updated.