Preemptively bump scijava-common, scijava-ui-swing
Migrate ImageJ-specific config to pom-imagej

See:
https://github.com/imagej/pom-imagej

Projects that want to manage their ImageJ version dependencies should
either extend pom-imagej, or include it using Maven's import scope
mechanism:

  <dependency>
    <groupId>net.imagej</groupId>
    <artifactId>pom-imagej</artifactId>
    <version>2.7</version>
    <scope>import</scope>
  </dependency>
Fix MiniMaven GitHub URL
Release version 2.0

This removes the groupId properties, bumps scijava-common and
scijava-ui-swing, and removes the ImageJ managed dependencies
(they migrated to pom-imagej).

If this approach works well, we'll migrate the ImgLib2 and SCIFIO
managed dependencies to their own parent POMs as well. In this way,
the pom-imglib2, pom-scifio and pom-imagej POMs can serve as examples
for how other projects can extend the SciJava POM as they see fit.