Fixes #5689 - Plugin permissions are migrated too

fixes #4806 add support to register compute resource provider from a plugin

fixes #5077 - refactor safemode rendering to allow helpers and variables from plugins

Fixes #4353 - plugins don't create permissions until DB is migrated

fixes #812 - new permissions model, user group role and nest support, role filters for better granularity

• Daniel Lobato <elobatocs@gmail.com>
• Joseph Magen <jmagen@redhat.com>
• Tom McKay <thomasmckay@redhat.com>
• Greg Sutcliffe <gsutclif@redhat.com>...

Fixes #3838: Adds ability to define a divider when declaring a menu item
from a plugin.

fixes #3772: a block is now optional when defining sub menus from foreman plugins

fixes #3510 - plugin interface for registering a plugin, updated menu system