add licenses from 3rd party frameworks / libs

[DonatJR]

fixes #43

• the license of the base64 lib is still missing
• the license folder should be distributed with the installer

@SailReal I will probably need your help with both of these points

[DonatJR]

Looks good 👍 (I can't approve my own PR ;)). Could you take a quick look at the final change I just made?