Fix: Validation errors is not shown when resetting password

- Retrieve data even for POST requests since it's needed for breadcrumbs
- Switch to Model::find() since Model::read() clears Model::$validationErrors

Closes #431
Fix: Infinite redirects for non-admin accessing /admin area

Valid users will get infinitely redirected to /admin/users/users/login
which they don't have access.  Grant access of this URL to public role to
prevent this.

Closes #431
Clears file_map when activating a theme/plugin

For themes providing its own CustomHelper, activating the theme
may cause missing method errors since it's still using
Croogo.View/Helper/CustomHelper.  Clear the file_map cache so that
it's immediately available.
Fix: Prevent undefined index errors in Nodes/admin_add

See croogo/croogo#199
Handle non-existent theme path for php 5.2

Closes #430