Don't assume sub-second timestamp granularity in ResourcesTest

Some operating systems or file systems may support file time stamps
with one second granularity. On such systems ResourcesTest.compare
would fail.
Added symlink test project
Removed mutating setters, cleaned up hierarchy. Bumped to 2.1-SNAPSHOT
Merge pull request #5 from mizdebsk/PLXCOMP-241

[PLXCOMP-241] Don't assume sub-second timestamp granularity in ResourcesTest
[PLXCOMP-117/PLXCOMP-64/PLXCOMP-113] Symlink support

Based on patch Zuhayr Khan, heavily modified and extended by me
Added headers
[maven-release-plugin] prepare release plexus-io-2.1
[maven-release-plugin] prepare for next development iteration
Restored jdk5 compatibility
[maven-release-plugin] prepare release plexus-io-2.1.1
[maven-release-plugin] prepare for next development iteration