refactor terraform modules, add clustering lambda (#4)

terraform/modules/alpr_clusters/variables.tf

@@ -0,0 +1,16 @@
+variable "module_name" {
+  description = "Name of the module"
+}
+
+variable "output_filename" {
+  description = "Filename for the ALPR clusters JSON file"
+  default     = "alpr_clusters.json"
+}
+
+variable "deflock_stats_bucket" {
+  description = "S3 bucket for the ALPR clusters JSON file"
+}
+
+variable "rate" {
+  description = "Rate at which to run the Lambda function"
+}