Fix various spelling mistakes throughout the code

7 jobs for master in 2 minutes and 24 seconds (queued for 1 second)
Status Job ID Name Coverage
  Test
passed #20051
allowed to fail
pylint-plugins

00:01:23

passed #20048
pytest-3.5

00:00:44

passed #20049
pytest-3.6

00:00:44

passed #20050
pytest-latest

00:00:41

passed #20047
security-check

00:00:32

 
  Build
passed #20052
www
build-doc

00:01:00

passed #20053
build-ubuntu

00:00:22