[Feature] Improve config:register_symbol function
[Feature] Improve config:register_symbol function

Now this function replaces all other registration functions and can
accept table for furhter extending

AlexeySa/rspamd,AlexeySa/rspamd,AlexeySa/rspamd,minaevmike/rspamd,minaevmike/rspamd,minaevmike/rspamd,andrejzverev/rspamd,andrejzverev/rspamd,AlexeySa/rspamd,minaevmike/rspamd,minaevmike/rspamd,minaevmike/rspamd,AlexeySa/rspamd,andrejzverev/rspamd,minaevmike/rspamd,andrejzverev/rspamd,andrejzverev/rspamd,minaevmike/rspamd,andrejzverev/rspamd,minaevmike/rspamd,andrejzverev/rspamd,AlexeySa/rspamd,AlexeySa/rspamd,AlexeySa/rspamd,andrejzverev/rspamd,AlexeySa/rspamd