update inline doc of config file; fix README conf ref

Author: Archit Sharma

README.md

@@ -88,7 +88,7 @@ If you think it's a bug, you're welcome to open an issue here on github.
 ### Additional Note
 
 - Below mentioned ports will be used for port mapping from container to host, and
-  could be configured in `sarjitsu.conf`. Default bindings are:
+  could be configured in `conf/sarjitsu.conf`. Default bindings are:
 
   ```sh
   METRICSTORE_PORT_MAPPING=9600

conf/sarjitsu.conf

@@ -10,12 +10,15 @@
 ###########################################################
 # metricstore config (postgres) - for grafana's metadata
 DB_HOST=
-# append DB_PORT in grafana.ini db config
 DB_NAME=grafana
 DB_USER=grafana
 DB_PASSWORD=sarjitsu123
-DB_PORT=5432 # default for postgres
+DB_PORT=5432
 
+# TODO: data dir option below is currently not integrated into sarjitsu;
+# one would have to build a postgres container, to make new mountpoint
+# available. Refer to https://hub.docker.com/_/postgres/ for more.
+# set to default
 DB_DATA_DIR='/var/lib/postgresql/data'
 # change this in production, if you have a fs mountpoint (for persistent disks)
 # if so, you'll have to build the postgres container (and not just pull it
@@ -25,13 +28,17 @@ DB_DATA_DIR='/var/lib/postgresql/data'
 # datasource config (elasticsearch) - source of timeseries data
 ES_HOST=
 ES_PORT=9200
+
+# sarjitsu currently needs passwordless access to elasticsearch;
+# this protocol goes into grafana's datasource settings.
 ES_PROTOCOL=http
 
 # set this if you want a particular cluster name while building
 # the ElasticSearch container. If not set, a random string will be assigned
 ES_CLUSTER_NAME=elasticsearch$RANDOM
 
-# below settings are for data sent to ES by backend and middleware
+# below settings are for data sent to ES by backend and middleware;
+# recommended to keep these values to default.
 INDEX_PREFIX=sarjitsu
 BULK_ACTION_COUNT=2000
 INDEX_VERSION=1
@@ -46,14 +53,24 @@ GRAFANA_DB_TYPE=postgres
 # make sure this is above 1024; 3000 is standard
 GRAFANA_PORT=3000
 
+# Sarjitsu supports only ES < 2.0 ..which supports _timestamp
+# in mapping. If you don't have a production instance of ES<2.0
+# it is highly recommended to leave ES_HOST option empty to let
+# sarjitsu spawn it's own compatible instance of ElasticSearch
 GRAFANA_TIMEFIELD=_timestamp
+
+# you could change these 
 GRAFANA_DS_NAME=elastic
+
+# don't change this. It is here for reference of app itself
 GRAFANA_DS_PATTERN=[$INDEX_PREFIX.sar-]YYYYMMDD
 
 ###########################################################
 # middleware config (frontend API server) - service that builds dashboards
 MIDDLEWARE_HOST=
 MIDDLEWARE_PORT=80
+
+# don't change this. It is here for reference of app itself
 MIDDLEWARE_ENDPOINT=/db/create/
 
 ###########################################################