DarkNight theme for Ghidra

There are still some "bugs" in the display, because actually we can't configure colors for everything :

• colors in the Symbol Tree window (function names are hard to read)
• background decompilation window when the cursor is in an undefined function
• selection in decompilation mode
• PCode
• graph window

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To install the theme, run the script :

./set_colors.py ~/.ghidra/.ghidra-9.0/tools/_code_browser.tcd