Add docker, DuckDuckGo, Dockerfile, asteval(math), logging

[nenkoru]

• A Dockerfile has been added in order to run the project much easier within a container.
• Changed import style of a project to namespace-alike. Improves readability of the project by import modules, instead of objects directly.
• Added duckduckgo as an available search backend.
• Added asteval as a safe evaluator of math expressions.
• Added basic config for logging

[nenkoru]

Closes #1