[feature] Action to set a feature as the current atlas feature - sponsored by SIGE

This work is kindly sponsored by SIGE (www.sige.ch). This request adds the concept of "standard actions" for a vector layer, which are predefined actions that are available for all vector layers. They are kept separate from the normal, user-defined actions to maintain the distinction from actions which are created and configurable by the user. 
This was done to allow for an action for setting a feature as the current atlas feature, which is useful for both previewing atlas based styling and for navigating to a specific feature in the new atlas preview mode.