[scripts] Enhance install.sh to merge pixels.properties updates without overwriting local values

[AntiO2]

Problem

install.sh currently asks whether to fully overwrite PIXELS_HOME/etc/pixels.properties when the file already exists.

This is inconvenient for upgrades: users often keep local value changes, but the template at pixels-common/src/main/resources/pixels.properties may add or remove config keys over time.

Expected behavior

If the local file does not exist, copy it as today.

If it exists, compare keys with the template and:

• list new config options
• ask whether to append them, default yes
• list deprecated local-only options
• ask whether to remove them, default no

This would preserve local values while making template config changes visible and easy to apply.

Preview: