Append support for textual net list

Added support for textual netlist

In the early days of SalixEDA, when SN74...-type chips were still widely used, the system had a textual netlist. It was a special object in the schematic that listed connections to nets in text form. Typically, this was used for connecting power nets.

1. Connect pins 14 of chips DD1, DD3 to net +5V.

This is the external representation of the netlist. Internally, such an entry was translated into connections between the corresponding chip pins.

When transitioning to the modern SalixEDA, this functionality was removed because at that time SN74...-type chips were practically no longer used in schematics, as the general trend toward higher integration made their use unnecessary. And in those cases where the use of such chips was still needed, the power net connection problem could be solved by adding a dedicated power section to multi-section components or by adding power lines directly to the component's schematic symbol — for single-section components.

And today this functionality has been brought back to SalixEDA, since the system is positioned as suitable for education, and in the process of teaching students, SN74...-type chips are still widely used. Therefore, to make it possible to design circuits with such chips in the familiar way, i.e., via a textual netlist, the "Text Netlist" object and the corresponding mode have been added to the SalixEDA system.