Implement Logger

[sukrutrao]

Implement a logger to display output with different severity and verbosity levels.

TODO

• [x] Logger
• [x] Verbosity level as command line input (where highest level would log all, lowest level would log only ERROR)
• [x] Add doxygen comments

[sukrutrao]

@prateekkumarweb

1. OK.
2. I planned to have other tangential tasks covered by logger, such as controlling verbosity or helping formatting text, where the "[]" type of label should not be there. The EMPTY level skips that, and is the default, so if only other options are passed, then there will be no severity-related effects in the output.
3. OK. Colour?

[sukrutrao]

@prateekkumarweb TODO complete.