Rename constants, variables, classes, methods, functions

Some ideas are in https://pad.riseup.net/p/rGfvR7ZsvtoZ.

It would be nice to create first a list of all the things to rename and the proposed new names.

It should be done file for file as possible and be reviewed/merged fast to avoid many merge conflicts.

Only a part of this was https://github.com/torproject/sbws/issues/202.