Deprecate duplicate function and make it use its replacement
Implement LogInPage.addLoginButton() which is needed for CreateIdentityWizard:
- Inspired by the Freetalk one but with several minor structural improvements
LogInPage code structure tweaks:
- Use WebInterfaceToadlet.getURI() instead of deprecated path()
- Don't store the URI in a member variable, we only use it once
- Don't hardcode the form name, use pagetTitle instead. Notice: Form names probably aren't even used for anything, so it is not a problem if this changes