Restore eclipse settings to stop m2e errors
Replaces references to 'files' with 'sources'

Replace references to 'files' throughout the code-base with 'sources'
following the rename of `FileOptions` to `SourceOptions`.

Also cleanup ResourceUtils a little
Revert "Allow maven build with JDK 1.8"

Revert commit fd15b62a9d36cf7f0c592f90283107671d758d32 to
ensure that we don't accidentally use Java 8 features.
Polish