Spurious "Ignoring unsupported script" debug messages on startup

[ctrueden]

Upon launching ImageJ2 with --debug from the CLI, amongst the usual deluge of messages, we now see:

[DEBUG] Ignoring unsupported script: bigwarp_fiji-7.0.7.jar
[DEBUG] Ignoring unsupported script: M_I_P-2.0.1.jar
[DEBUG] Ignoring unsupported script: IO_-4.2.1.jar
[DEBUG] Ignoring unsupported script: SPIM_Registration-5.0.25.jar
...

for every JAR file in Fiji's plugins folder.

This suggests there is a problem with which folders are being scanned by the SciJava ScriptFinder—it is not supposed to be looking in the base plugins folder.