Various cleanup to help with maintenance / release process

[hazendaz]

• Dropped old contributors list as not valid place to store that these days. The user list there is mostly unrecognized contributors from long ago. Since we have used git for ~10 years if not more, no reason to store such data as the commit history shows all that. Also believe history was exported for google code so it should also have that information per commit.
• Remove the pre java 16 profile as we require java 17+
• Drop derby version in java16+ as we require 17 and the default is already set for java17+
• Add some adjustments (also added to parent for 49 release) that allow us to release this without messing with extra flags.

Upon this build will effectively build java 8 compliant code without thinking about it.

[coveralls]

coverage: 87.171% (-0.01%) from 87.183%
when pulling 551ba16 on hazendaz:pom-cleanup
into d20ac1d on mybatis:master.