Simplify adding rules

[RaduNico]

Adding new rules to the project is a fairly complex process that needs editing the rules file.

It should be possible to add rules from the backend administrative interface based on existing rule types. Current rule types are scrambler, wordlist, john, generated, mask_hashcat, filemask_hashcat.

Creating additional rule types will still be a process that needs editing files and code, but could be made easier by treating rules as generically as possible and adding specific code where needed, preferably in a separate file. Could be made even simpler by treating rule types as addable modules with standardized function calls.