Coding style: Always ensure Cache.initLogger() called to avoid Unexpected null pointer exceptions when using jalview.bin.Cache.log

More of an informational than anything else. Whilst testing JAL-3628 I noticed that many tests were being skipped due to a buried NullPointerException occuring in odd places:

$ gradle clean test
...
> Task :test

jalview.ws.sifts.SiftsClientTest.setUpSiftsClient FAILED
    java.lang.NullPointerException at SiftsClientTest.java:201

jalview.analysis.FinderTest.tearDownAfterTest FAILED
    java.lang.NullPointerException at FinderTest.java:85

jalview.analysis.FinderTest.tearDownAfterTest FAILED
    java.lang.NullPointerException at FinderTest.java:85

jalview.analysis.FinderTest.tearDownAfterTest FAILED
    java.lang.NullPointerException at FinderTest.java:85

jalview.analysis.FinderTest.tearDownAfterTest FAILED
    java.lang.NullPointerException at FinderTest.java:85

jalview.analysis.FinderTest.tearDownAfterTest FAILED
    java.lang.NullPointerException at FinderTest.java:85

jalview.analysis.FinderTest.tearDownAfterTest FAILED
    java.lang.NullPointerException at FinderTest.java:85

jalview.analysis.FinderTest.tearDownAfterTest FAILED
    java.lang.NullPointerException at FinderTest.java:85

jalview.analysis.FinderTest.tearDownAfterTest FAILED
    java.lang.NullPointerException at FinderTest.java:85

jalview.analysis.FinderTest.tearDownAfterTest FAILED
    java.lang.NullPointerException at FinderTest.java:85

jalview.analysis.FinderTest.tearDownAfterTest FAILED
    java.lang.NullPointerException at FinderTest.java:85

jalview.analysis.FinderTest.tearDownAfterTest FAILED
    java.lang.NullPointerException at FinderTest.java:85

jalview.analysis.FinderTest.tearDownAfterTest FAILED
    java.lang.NullPointerException at FinderTest.java:85

jalview.analysis.FinderTest.tearDownAfterTest FAILED
    java.lang.NullPointerException at FinderTest.java:85

jalview.analysis.FinderTest.tearDownAfterTest FAILED
    java.lang.NullPointerException at FinderTest.java:85

1331 tests completed, 15 failed, 1316 skipped

> Task :test FAILED

All these NPEs are where jalview.bin.Cache.log is being used. In this case, I discovered the root cause was a patch introduced via JAL-3628, where a static method (jalview.io.BackupFiles.moveFileToFile(..)) was using jalview.bin.Cache.log without first calling Cache.initLogger().

This didn't cause any problem until one of the '.sifts_downloads' files became too old, trigging a call to update the SIFTS file cache.. which due to another patch introduced in JAL-3628 called BackupFiles.moveFileToFile without initting the logs.