Add basic "create" API..

.. using server-side API tokens

capsulflask/schema_migrations/16_down_api_tokens.py

@@ -0,0 +1,2 @@
+DROP TABLE api_keys;
+UPDATE schemaversion SET version = 15;

capsulflask/schema_migrations/16_up_api_tokens.py

@@ -0,0 +1,9 @@
+CREATE TABLE api_tokens (
+  id                 SERIAL PRIMARY KEY,
+  email              TEXT REFERENCES accounts(email) ON DELETE RESTRICT,
+  name               TEXT NOT NULL,
+  created            TIMESTAMP NOT NULL DEFAULT NOW(),
+  token              TEXT NOT NULL
+);
+
+UPDATE schemaversion SET version = 16;