add middleware to be able to expire inactive sessions after N seconds

configure middleware

add test for session inactive timeouts

add Studio inactive session timeout test

change login method used

add create_test_account to test

make sure the expected redirect URL is right

fix indenting problem

fix doc string since we moved from minutes to seconds

use utility methods rather than calling another test to set up and activate an account

clean up code violations

respond to PR feedback

use optional params to make code cleaner

pylint fix on test files
Merge pull request #2278 from edx/cdodge/session-inactivity-timeout

add middleware to be able to expire inactive sessions after N seconds