Allows changing of bot configuration values without needing to restart
bot instance or needing to edit pbot.pl script.
Registry will initially be populated with default values from pbot.pl,
but if a registry file exists then the registry values will take
precedence over the pbot.pl values. For instance, if you regset the
bot trigger to '%' then the trigger will be '%' even if pbot.pl has '!'
or something else explicitly set.
Some registry items can have trigger hooks associated with them. For
instance, the irc->botnick registry entry has a change_botnick_trigger
associated with it which changes the IRC nick on the server when a new
value is set via regset/regadd.
Tons of other fixes and improvements throughout.
