Make the build reproducible

This bumps to pom-fiji 5.0.6, which upgrades the 3D_Viewer
component to 3.0.1, its first non-tainted release.

It eliminates the following errors:

    $ mvn org.scijava:scijava-maven-plugin:0.3.0:verify-no-snapshots
    [ERROR] Could not resolve dependency: Dependency {groupId=sc.fiji, artifactId=fiji-lib, version=2.0.0, type=jar} of path:
            sc.fiji:VIB-lib:2.0.0
            sc.fiji:3D_Viewer:3.0.0
            sc.fiji:Simple_Neurite_Tracer:2.0.3-SNAPSHOT
    [ERROR] Found SNAPSHOT version:
            sc.fiji:pal-optimization:2.0.0-SNAPSHOT
            sc.fiji:VIB-lib:2.0.0
            sc.fiji:3D_Viewer:3.0.0
            sc.fiji:Simple_Neurite_Tracer:2.0.3-SNAPSHOT
    [ERROR] Found SNAPSHOT parent:
            sc.fiji:pom-fiji:2.0.0-SNAPSHOT
            sc.fiji:pal-optimization:2.0.0-SNAPSHOT
            sc.fiji:VIB-lib:2.0.0
            sc.fiji:3D_Viewer:3.0.0
            sc.fiji:Simple_Neurite_Tracer:2.0.3-SNAPSHOT
Bump to next development cycle

Signed-off-by: Curtis Rueden <ctrueden@wisc.edu>
Bump to pom-fiji 5.1

Adds deep SNAPSHOT check enforcer rule.

Prevents future releases from being tainted by snapshot
dependencies.