Provide script to assign a role to a resource

[mbraekman]

Is your feature request related to a problem? Please describe.
Since the current script New-AzResourceGroupRoleAssignment only allows for the creation of a new role assignment to a resource group, a separate script New-AzResourceRoleAssignment should be created to assign a new role based on the ObjectId or ResourceGroupName/Resource-combo to a specific resource.

Describe the solution you'd like
The script should accept the following parameters:

• TargetResourceGroupName (mandatory)
• TargetResourceName (mandatory)
• TargetResourceType (mandatory)
• RoleDefinitionName (mandatory)
• ObjectId
  OR (see Provide functionality to assign a role to a resource group based on the ObjectId #150)
• ResourceGroupName AND ResourceName

Describe alternatives you've considered
Extend the existing function, however then the name should be changed, which means introducing a breaking change.