Add new preference option 'console.head_padding'

[Junology]

The PR adds console.head_padding preference option to configure blank lines printed in terminal/console in each time a sketch is run.

The background is found in #911.

Making the change, I originally planned to only add an option for backward compatibility.
However, I finally decided to rewrite the code for "padding by blank lines" using EditConsole.message instead of System.out.println to stop printing them in the terminal.
The reasons why I think this is safe are as follows:

1. First of all, the change only affects the IDE (i.e. processing) and not command-line mode (i.e. processing-java).
   Hence, it would not affect the final products of any projects using Processing either.
2. Windows: after investigation, I realized that the blank lines does not affect Windows terminals (i.e. command prompt or PowerShell) probably because of launch4j.
   So, maybe it would not seriously break backward compatibility in Windows if the blank lines are removed.
3. Linux: processing is run as a background process, so any outputs can mess up the terminal.
   Moreover, since the blank lines are likely the only outputs from IDE (NOTE: print/println does not print to terminal from IDE), so I think nobody rely on the behavior.

Unfortunately, I have not tested on MacOS and cannot since I don't have any machines.
It would be great if someone tests the change of behavior on MacOS and gives comments.

I also note that, in spite of my comments in #911, the head padding may be useful when console.auto_clear option is set to false.
For example, the following code prints HelloHelloHello without line breaks if you run it three times with console.auto_clear = false and console.head_padding = 0 on your preferences.txt:

print("Hello");

I wonder if console.auto_clear and the new option console.head_padding are worth putting in the preference dialog.
In some situations, keeping console outputs may help debugging, but currently nobody knows the option.

[Stefterv]

Thank you for your contribution @Junology! I'm happy to add it and thank you for documenting your work thoroughly!

If you have a bit more time, please check the try catch otherwise this is good to go!