[Column List][Bom][Added] Added 'Net Label' column

[nguyen-v]

This PR adds a new column Net Label, which is similar to to Net Name but without the path. Only displays the Net Label given in the schematic. For example, for the nets:

/Project Architecture/MCU - IOs/MOTOR_ENABLE
/Project Architecture/MCU - IOs/MOTOR_HIZ
/Project Architecture/MCU - IOs/MOTOR_FAULT
/Project Architecture/MCU - IOs/DRV_SCLK
/Project Architecture/MCU - IOs/DRV_MISO

Net label would be:

MOTOR_ENABLE
MOTOR_HIZ
MOTOR_FAULT
DRV_SCLK
DRV_MISO

If there is no '/', just keep it as is, for example:
+3V3 would stay +3V3

This is useful when creating simplified testpoint lists in a large hierarchical schematic, where the path can get very long.

[nguyen-v]

Not sure how to handle the 'Invalid column name' warning, I don't know if this new column should be added to the extra columns as it is inherently redundant with Net Name

[set-soft]

Thanks!
I added it to the "extra" columns, they are used to detect bogus names and for examples. A redundant column in an example isn't bad.