Creates a layer. For more information, see How to Create a Layer (http://docs.aws.amazon.com/opsworks/latest/userguide/workinglayers-basics-create.html).
You should use CreateLayer for noncustom layer types such as PHP App Server
only if the stack does not have an existing layer of that type. A stack can have at most one instance of each noncustom layer; if you attempt to create a second instance, CreateLayer fails. A stack can have an arbitrary number of custom layers, so you can call CreateLayer as many times as you like for that layer type.
Required Permissions: To use this action, an IAM user must have a Manage
permissions level for the stack, or an attached policy that explicitly grants permissions. For more information on user permissions, see Managing User Permissions (http://docs.aws.amazon.com/opsworks/latest/userguide/opsworks-security-users.html).