Move interfaces to own files and provide type declarations

[tripodsan]

The current log.js is quite large and contains a log of functions and classes.
IMO, at least the interfaces that are not tried to the log module should be refactored in their own files.

An additional bonus would be to provide typescript like type declarations.

[koraa]

Good idea! I have tried splitting log.js multiple times and ran into circular dependency issues.
Maybe you will have more luck!

I think typescript declarations would be a good idea too; should be a separate issue though unless you really want to tackle both at once. If we do that we might provide proper type script interfaces right away…