api: Updates to Makefile and configuration files.

- Re-organized and documented make targets.
- Parameterized the make targets to more cleanly support multiple
  development scenarios.
- Documented the different development scenarios in a README.
- Standardized the host port used when running locally.
- Updated DEV and PROD database config files to match current practice.
- Renamed `personal_measure_api.config.prod.json` to
  `personal_measure_api.config.docker.json` to more accurately reflect
  that this is the config used when building the docker image
  (regardless of which env it ends up in).

api/personal_measure_api.config.json

@@ -2,7 +2,7 @@
   "authSecret":"bifekHuffIs3",
   "dbConnString":"host=localhost port=5500 dbname=personal_measure user=postgres password=password",
   "debug":true,
-  "port":8081,
+  "port":8100,
   "pwdCost":11,
   "knownOrigins": [ "https://curl.localhost" ]
 }