Imported from archive.

* command (control), menu (control): Locked these files to be
read-only, for added security.

* mudpy.conf (categories, control, include): Moved categories and
include elements to be control meta-element list facets called
default_files and include_files respectively, allowing them to be
utilized in multiple files within the data tree.
(control): Added a list facet called private_files which works like
default_files but creates them mode 0600, and moved the accounts
file to this list to prevent leaking MD5 password hashes for
accounts.
(internal:general): Renamed to internal:limits and added a
max_avatars int facet providing the means to cap the number an
account is allowed to have.

* mudpy.py (Element.get, Element.getdict, Element.getfloat)
(Element.getint, Element.getlist): Reworked to provide a means to
override the default values through a function parameter, similar to
getboolean.
(Element.set): Strip trailing L off long ints.
(handler_checking_new_account_name): Abstracted this entire function
out into the checking_new_account_name menu configuration.