Option to disable or uninstall unneeded modules

[joshuarestivo]

Now that Frappe CRM and Frappe Helpdesk are beginning to integrate with ERPNext, it's necessary to clean up the 'legacy' CRM and Support modules in ERPNext. Having ERPNext installed on the same system as Frappe CRM or Frappe Helpdesk can get overly confusing (eg., CRM vs FCRM doctypes and the various entangled permissions). If the original modules are not going to be removed from ERPNext in the near future, there should be an option to disable them or, at minimum, avoid having their installation.