[Lazarus] New compiler options page "Additions and Overrides"

[Juha Manninen]

The build mode edit window, opened from the '...' button, could have a
button for creating the Debug and Release modes.
They would not exist by default but one could create them with minimal effort.

Still, the GUI must be designed to be as intuitive as possible with
build modes defined.
Mattias suggested an option for hiding the new grid GUI.
The option must be more generic, affecting all necessary places.
The <All build modes> was an idea for such option, but it could also
be a checkbox "Advanced build mode editing" or similar.
The same setting would allow editing paths for many build modes.

Juha