Ban time incr

New feature "automatically exponential increasing ban time".
WARNING: by first start the server upgrades sqlite database (table "bans" will recreated with another schema);
Option "bantime.increment" in jail.conf allows to use database for searching of previously banned ip's to increase a default ban time using special formula, by default each next ban increase banTime * 1, 2, 4, 8, 16, 32...
see "jail.conf" for some other options of "bantime.___";
additional we can configure a little randomization of ban time, to prevent "clever" botnets calculate exact time IP can be unbanned.

FWIW I also had similar feeling... @sebres did provide some good reasoning at some point but I do not remember still being convinced... IMHO we could simply hardcode a formula, may be even the exponent base and maxretries then being a list of multipliers for the exponents (with negative or 0 being for permanent)