refactor e2e settings and config modules

This should make the settings and configuration logic less implicit and
a little easier to follow. Some familiarity with the configuration behavior
of nightwatch is still necessary in places - specifically, one should know
that all test_settings defined for non-default environments are treated as
overrides to the values defined for the default environment.

awx/ui/test/e2e/tests/test-credentials-add-edit-machine.js

@@ -1,5 +1,7 @@
 import uuid from 'uuid';
 
+import { AWX_E2E_TIMEOUT_LONG } from '../settings';
+
 const testID = uuid().substr(0, 8);
 
 const store = {
@@ -169,7 +171,7 @@ module.exports = {
         const row = '#credentials_table tbody tr';
 
         credentials.section.list.section.search
-            .waitForElementVisible('@input', client.globals.longWait)
+            .waitForElementVisible('@input', AWX_E2E_TIMEOUT_LONG)
             .setValue('@input', `name:${store.credential.name}`)
             .click('@searchButton');