Visibility of microflows and nanoflows

Hi,

Just like in normal code, it should be possible to define a visibility for our microflows and nanoflows :

• public : would be used by default : the microflow/nanoflow can be used from anywhere ; this is the current behavior
• module : only
• folder : only visible from the same folder

This would improve the organization of microflows and nanoflows in the code, and help also when we import thirdparty modules