Adds 'pluginstofile' command for better admin life

The command 'pluginstofile' writes a file into the 'pluginsreports'
folder, which contains all plugins with their version and authors.

An optional argument can be passed as the file name. If no file name is
specified, then the current date and time is taken.

The permission for the command is: libigot.command.pluginstofile and is
available normally to operators.

Signed-off-by: XemsDoom <moser.luca@gmail.com>