- buttons_toolbar: now expect links represented by an array instead of HTML content
- fields_toolbar: now expect a form represented by an array instead of HTML content
- action_plugin: now expect links represented by an array instead of HTML content
Default templates updated accordingly
mprove theme dependent plugin placeholders:
All plugins can optionally add an init function named `pluginname_init()` which is called when the plugin is loaded.
This function is aware of the config, and can return initialization errors, which are displayed in the header template.
Note that the previous error system hack no longer work.
