Use SoftReference for CloverBuildAction.report to avoid reloading results constantly.
Merge branch 'master' into CloverBuildAction.report-SoftReference

Conflicts:
	src/main/java/hudson/plugins/clover/CloverBuildAction.java
Merge branch 'master' into CloverBuildAction.report-SoftReference
Switching to a 15min timeout rather than using SoftReference.
Merge pull request #12 from jglick/CloverBuildAction.report-SoftReference

Use Guava's CacheBuilder with weakKeys() for CloverBuildAction.report to avoid reloading results constantly.