Improve buffer-pool model description

[standalone@localhost:9990 /] /subsystem=io/buffer-pool=foo:read-resource-description
{             
    "outcome" => "success",
    "result" => {
        "description" => "Defines buffer pool",
        "capabilities" => [{
            "name" => "org.wildfly.io.buffer-pool",
            "dynamic" => true
        }],
        "attributes" => {
            "buffer-size" => {
                "type" => INT,
                "description" => "The size of each buffer slice in bytes, if not set optimal value is calculated based on available RAM resources in your system.",
                "expressions-allowed" => true,
                "required" => false,
                "nillable" => true,
                "access-type" => "read-write",
                "storage" => "configuration",
                "restart-required" => "all-services"
            },
            "buffers-per-slice" => {
                "type" => INT,
                "description" => "How many buffers per slice, if not set optimal value is calculated based on available RAM resources in your system.",
                "expressions-allowed" => true,
                "required" => false,
                "nillable" => true,
                "access-type" => "read-write",
                "storage" => "configuration",
                "restart-required" => "all-services"
            },
            "direct-buffers" => {
                "type" => BOOLEAN,
                "description" => "Does the buffer pool use direct buffers, some platforms don't support direct buffers",
                "expressions-allowed" => true,
                "required" => false,
                "nillable" => true,
                "access-type" => "read-write",
                "storage" => "configuration",
                "restart-required" => "all-services"
            }
        },
        "operations" => undefined,
        "notifications" => undefined,
        "children" => {}
    }
}