Change license to LGPL

[nexy7574]

This pull request is a request for comments regarding our license.

When the nio-bot project was first created, the GPLv3 license was chosen. However, after further research, I believe LGPLv3 is better suited to the project.

If anyone happens to have any concerns, questions, or comments, please leave them in this PR. Assuming all (if any) conflicts are resolved, this pull request will be merged within a week.

(Ignore the first/sole commit saying AGPL from GPL, I meant LGPL but got mixed up.)

[nexy7574]

Changed the PR title to add clarification

We will be moving from the less permissive GPL, to the more permissive LGPL

The key differences in this license change would be that you are free to distribute your own code under any license, so long as this project retains its license (i.e. you have to disclose any changes & provide a link to the modified source if you were to modify an installation of NioBot).
As it stands, due to the GPLv3 license being used, you have to license your project under GPLv3 too, which is not ideal when this is just a library you can use, not a project itself.