MiniMaven: look into ImageJ's catch-all repository first of all

We worked a little bit on making ImageJ's Maven repository even more
useful than it already was, by making its 'public' repository include
even more cached artifacts.

Let's use it.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
MiniMaven: fix metadata path for -SNAPSHOT versions

Previously, if the snapshot version information filled in correctly,
MiniMaven looked in the wrong place for maven-metadata-snapshot.xml.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
MiniMaven: report the path when XML parsing failed

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
MiniMaven: handle more maven-metadata-snapshot.xml formats

Jori Jenkins just encountered this maven-metadata-snapshot.xml:

	<?xml version="1.0" encoding="UTF-8"?>
	<metadata>
	  <groupId>org.scijava</groupId>
	  <artifactId>native-lib-loader</artifactId>
	  <version>2.0-20131121.164942-1</version>
	  <versioning>
	    <snapshot>
	      <buildNumber>1</buildNumber>
	    </snapshot>
	  <lastUpdated>20131121172100</lastUpdated>
	  </versioning>
	</metadata>

Let's teach MiniMaven to parse that, too.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>