R1872 Can't exit "Select Main Component" mode for package.

I tried to create a new package.

From it's context menu I choosed "Select Main Component".

Under that mode I can click components and the one that get clicked will switch from yellow masked/unmasked.

Issues:
- I can't find a way to exit that mode. It seems that compSelected(NULL) is not correctly handled.

- It seems that mutiple components can be selected. Maybe the action should be named as "Select Main Components?"

- What's the usage of main component?

I tried to create a new package.

From it's context menu I choosed "Select Main Component".

Under that mode I can click components and the one that get clicked will switch from yellow masked/unmasked.

Issues:
- I can't find a way to exit that mode. It seems that compSelected(NULL) is not correctly handled.

- It seems that mutiple components can be selected. Maybe the action should be named as "Select Main Components?"

This feature was modified recently and is still in "experimentation" process.
To exit it use mouse right-click.

- What's the usage of main component?

It is used in subcircuits when you need to access components inside the subcircuit.
An example is Arduino boards: you need to access the MCU inside to load firmware, Mcu Monitor, and other features.

I reorganized this a bit, and did some modifications (R1879):

- To stop linking/main_component: Right-click | Click on circuit canvas | Esc key.

- Dedicated icon for linking/main_component, so it is clear when we are in this mode.