4056-add smart defaults for recaptcha settings
4056-add smart defaults for recaptcha settings

If RECAPTCHA_* configuration options are not present in bridgedb.conf,
bridgedb disables recaptcha support.

wfn/bridgedb,pagea/bridgedb,sysrqb/bridgedb,pagea/bridgedb,wfn/bridgedb,mmaker/bridgedb,aagbsn/bridgedb,mmaker/bridgedb