option to control userfile changes with sharing flags (Bug #59)

[Ben Dover]

add option to control changes to user files
a bot would reject any userfile changes unless the bot requesting the change is
set botattr +p

this would prevent a remote slave bot from altering the master bot's user files.

global-* are not the answer. they can only be used on the top master.

with multi-level linking, allowing the +p flag to control changes would allow
intermediate bots to reject changes from slave bots linked to them but allow
changes from the upstream master bot.

provides more protection from a less secure slave bot from being hacked and used
to make mass changes on the secure master bot's records.