Bug fixes

Changes since 7.x-1.3:

• #2923727: Callback function is using include instead of require_once

• Issue #2924150 by COBadger: Add information about where user id, token secret can be found / created
• Issue #2925273 by Loparev: Submission progress is reset to 0 after translation downloading

• #2923527: Undefined index: menu_name in menu_item_extras_preprocess_menu()
• #2921845: Suggestions for theme menu_levels

Fixes #2924375: Displaying the units availability management json path error

The alpha2 release for user_registrationpassword.

The code is very close to a more stable 'beta' release, but bugs can exist and new features will be implemented before the final 1.0. So expect code to change after this release, but nothing to radical. Please test, review and provide feedback in the issue queue.

Notable changes so far:
- Move to unit test framework
- Install/uninstall hooks got ported and coding standards are all fixed
- Multiple (minor) issues and tasks, deprecated functions are all replaced