Only accept $_GET for logout parameter

Refs #462
Put the username in the masthead

Put the username in the title of the masthead so it can be retrieved
for tests.
Use it in setting school permissions.
Expand Change School feature test

The change school drop down is actually on several controllers so this
expands the test to run on each of them and not lock ourselves into the
Home tab.
Only accept $_GET for schoolselect

Update controllers with school selectors to use get instead of get_post
method for fetching input.
Use get/post for course_management

Replace all calls to get_post with either get or post specifically.
Replace calls to get_post in calendar_controller

Replace all calls to get_post with either get or post specifically.
Replace calls to get_post in dashboard_controller

Replace all calls to get_post with either get or post specifically.
Replace calls to get_post in group_management

Replace all calls to get_post with either get or post specifically.
Replace get_post calls in web_controller

Replace all calls to get_post with either get or post specifically.
Replace get_post in instructor group management

Replace all calls to get_post with either get or post specifically.
Replace get_post in learning_materials controller

Replace all calls to get_post with either get or post specifically.
Replace get_post in management_console

Replace all calls to get_post with either get or post specifically.
Replace all get_post calls in offering_management

Replace all calls to get_post with either get or post specifically.
Replace all get_post calls in program_management

Replace all calls to get_post with either get or post specifically.
Merge pull request #587 from jrjohnson/462-inputsource

Replace all calls to get_post with either get or post specifically