Bump to next major version: 6.0.0-SNAPSHOT

This marks the BOM as backwards-incompatible. This should have been done
as part of 6264e74. I was somehow
thinking that the bump of scijava-config to 2.0.0 would not be backwards
incompatible from a BOM perspective. However, my thinking was fuzzy and
I cannot really justify it clearly -- better to be consistent and follow
the rule that minor dependency version bump(s) yield a minor BOM version
bump, and ditto for major version bumps.

Author: ctrueden

pom.xml

@@ -4,7 +4,7 @@
 
 	<groupId>org.scijava</groupId>
 	<artifactId>pom-scijava</artifactId>
-	<version>5.11.1-SNAPSHOT</version>
+	<version>6.0.0-SNAPSHOT</version>
 	<packaging>pom</packaging>
 
 	<name>SciJava Projects</name>