Add influxDB and Grafana images

grafana/Dockerfile

+FROM grafana/grafana:5.2.4
+
+USER grafana

grafana/README.md

+# Grafana
+
+Grafana is a metrics visualization software. Picasoft use it to show some stats from our services. This image is basically just a copy of the one from Docker Hub.
+
+## Configuration
+There are some evironment variable you can use to configure the instance :
+- `GF_DEFAULT_INSTANCE_NAME` : Name of your Grafana instance
+- `GF_SERVER_ROOT_URL` : Root URL of your Grafana instance (eg. `https://grafana.picasoft.net`)
+- `GF_SECURITY_ADMIN_USER` : Admin user
+- `GF_SECURITY_ADMIN_PASSWORD` : Admin password
+
+## Data persistence
+In order to ensure data persistence for your Grafana datasources and dashboard, you should mount a volume on `/var/lib/grafana`. Because Grafana is not execute as root user, you need to specify correct access right to this volume. Is using bind mount, you should do something like `mkdir volumes/grafana && chown 472:472 volumes/grafana`.

influxdb/Dockerfile

+FROM influxdb:1.6-alpine
+
+MAINTAINER kyane@kyane.fr

influxdb/README.md

+# InfluxDB
+
+InfluxDB is a time series database. Picasoft use this FOSS TSDB to store some metrics about its services. This image is basically just a copy of the official one from Docker Hub.
+
+## Configuration
+To automatically create a database at startup, set this environment variable :
+- `INFLUXDB_DB` : `DATABASENAME`
+
+### Authentication
+It is **really important** to properly configure authentication for InfluxDB HTTP API. First, to enable it, you should set this environment variable :
+- `INFLUXDB_HTTP_AUTH_ENABLED` : `true`
+
+Also, you need to use following environment variables in order to create some users :
+- `INFLUXDB_ADMIN_USER` : An admin user, use for administration purpose only
+- `INFLUXDB_ADMIN_PASSWORD` : Password for admin user
+- `INFLUXDB_WRITE_USER` : A user that can be used to write data to your database
+- `INFLUXDB_WRITE_USER_PASSWORD` : Password for the write user
+- `INFLUXDB_READ_USER` : A user that can be used to read data from your database
+- `INFLUXDB_READ_USER_PASSWORD` : Password for the read user
+
+## Data persistence
+In order to ensure data persistence for your database, you should mount a volume on `/var/lib/influxdb`