Modularize for JPMS

[jrb0001]

The PR has two commits and I recommend reviewing them individually:

• Packaging changes to create a multi-release jar file that works on Java 6+ and is a proper JPMS module (Java 9+). This bumps the minimum javac version to 9 but the resulting jar should work on Java 6 (untested).
• Remove the runtime dependency on the java.desktop module. This allows producing smaller runtime images if you don't need the terminal emulator parts nor the TextColor.getColor() method.

I tested it on Java 11 with a modularized version of the OutputString example both with and without the java.desktop module.

Is the package com.googlecode.lanterna.bundle meant to be used directly by the application/other libraries? If not, then its exports should be dropped.

[jrb0001]

Please note that this breaks WindowsTerminal if lanterna is used on the modulepath instead of the classpath. One way to solve that would be #422 and the alternative would be to move it to its own package and then use SPI to load it.

SPI sound like the better approach to me because that would also allow moving the terminal emulator part into its own module with proper runtime dependencies to java.desktop.

[mabe02]

I don't care too much about breaking the experimental, unfinished native bindings