Add drip file transformers

- for all three file functions on the drip contract

db/migrations/1536603967_create_drip_file_tables.down.sql

@@ -0,0 +1,3 @@
+DROP TABLE maker.drip_file_ilk;
+DROP TABLE maker.drip_file_repo;
+DROP TABLE maker.drip_file_vow;

db/migrations/1536603967_create_drip_file_tables.up.sql

@@ -0,0 +1,30 @@
+CREATE TABLE maker.drip_file_ilk (
+  id            SERIAL PRIMARY KEY,
+  header_id     INTEGER NOT NULL REFERENCES headers (id) ON DELETE CASCADE,
+  ilk           TEXT,
+  vow           TEXT,
+  tax           NUMERIC,
+	tx_idx        INTEGER NOT NUll,
+  raw_log       JSONB,
+  UNIQUE (header_id, tx_idx)
+);
+
+CREATE TABLE maker.drip_file_repo (
+  id SERIAL PRIMARY KEY,
+  header_id INTEGER NOT NULL REFERENCES headers (id) ON DELETE CASCADE,
+  what      TEXT,
+  data      NUMERIC,
+  tx_idx    INTEGER NOT NULL,
+  raw_log   JSONB,
+  UNIQUE (header_id, tx_idx)
+);
+
+CREATE TABLE maker.drip_file_vow (
+  id SERIAL PRIMARY KEY,
+  header_id INTEGER NOT NULL REFERENCES headers (id) ON DELETE CASCADE,
+  what      TEXT,
+  data      TEXT,
+  tx_idx    INTEGER NOT NULL,
+  raw_log   JSONB,
+  UNIQUE (header_id, tx_idx)
+);