Node template support, network support

[stefandevo]

This PR contains support for :

This allows you to set your ip range and subnet for private network:
#2

variable "ip_range" {
    type = string
    default = "172.16.0.0/12"
    description = "Ip Range to use for setting up Hetzner network."
}

variable "subnet_ip_range" {
    type = string
    default = "172.16.1.0/24"
    description = "Subnet Ip Range to use for setting up Hetzner network."
}

Extra parameters for the node-init:
Solving #10

variable "use_private_networks" {
  type = bool
  default = false
  description = "Use private network in node templates."
}

variable "node_cloud_init_path" {
    type = string
    default = ""
    description = "Path to the cloud init user data for node templates."
}

variable "node_template_types" {
    type = list(string)
    default = ["cx", "cx-ceph", "cpx", "ccx"]
    description = "All server types for which a node template will be created"
}

variable "node_template_zones" {
    type = list(string)
    default = ["nbg1", "fsn1", "hel1"]
    description = "All zones for which a node template will be created."
}

The node init will create by default ALL possible nodes, but with the above variables you can choose from zones and type combination.

Please note that #11 private network checkbox is not working.

[stefandevo]

Sorry, but I could figure out how to squash my commits... so this is basically what was in #12

[AmreeshTyagi]

any plan to merge this PR?