Add utility to check if some string value can be 'casted' to true or false.
slapgrid: Don't check root if we don't want to.
slapformat: Don't check root if we don't want to.
Remove useless chack in legacy code.
format: don't assume alter_user or alter_network.

It is assumed when arguments and config parameters are merged.
Otherwise, it is not possible to set this option from the .cfg.
format: Add safety check for speed hack.

Also put out the speed hack from the core code.