[add][paper] Survey and Comparison of Open Source Time Series Databases

## Type of action

- add

## Content

[Survey and Comparison of Open Source Time Series Databases](https://dl.gi.de/handle/20.500.12116/922)

## Category

Paper

![grafik](https://user-images.githubusercontent.com/1366654/39229450-1da12180-4863-11e8-89f8-7105f6b25713.png)

## Reason (Optional)

add: this paper presents a survey on existing TSDBs and describes their features.
