Add test logger

[nofun97]

Add test logger for testing the log messages of code. The API needs to be something that can be used to assert values instead of just recording the whole log. Current plan:

1. Have it be able to assert Fields
2. Assert message
3. Assert time (not important but nice to have)
4. Assert codelinker (after Add codelinker #10)
5. Assert level

[nofun97]

When this is fixed, feature from the PR #32 will have to be reverted. SetOutput creates problems as some loggers may not have an output (e.g. null logger).