Feature: Add support for user configurable custom roles

[pghildiyal]

Summary

Companies should be able to expand the roles which are currently available in Devtron, at the lease need two more roles - one with access to edit cluster information, other with access to only edit the configuration

Motivation

Different organizations may want to provide different level of access to their users. For eg some companies may be ok with giving terminal access to users who have deployment access while others may want to give it only to people who have edit config access.

AB#456