Removed compilation warnings and corrected typos

Removes all warnings at the compilation. Most warnings were straightforward to remove (unused imports, == instead of ===, redeclared variables...) and should not change the functionalities (except for one that I left unchanged).

All tests are still passing (except the periodicRefresher one we discussed about) but you might want to check yourself.

Oh and we might want to put a config file in the repo for prettier as my run of formatAllFiles gave a different formatting than what was already there.