Persistent modules

[ffredyk]

When merged this pull request will:

• Add a new parameter to zen_custom_modules_fnc_register for module persistency.
• Add a condition inside the custom module initialization function to remove only non-persistent modules.

PR for #577

[mharis001]

One problem with this is that the module does not have the correct name, category, or icon in the entities tree.

[ffredyk]

@mharis001 well I am not going to try and implement that kind of UI hacking, so if nobody else is up for the job, you could at least let it slide undercover and not list it publicly as a official supported function. This little change however, will greatly expand custom module possibilities and I personally would not mind the incorrect information inside the entities tree.

[mharis001]

The module isn't passed as a parameter to the function. Also, if the user code really needs a logic object, it can create one. Need to think more about this.