POM: bump to pom-imagej 2.48

This updates the version of several components:
* imagej-common -> 0.8.2
* imagej-legacy -> 0.8.2
* imagej-updater -> 0.6.1
* scijava-plugins-commands -> 0.1.7

Among other things, this fixes a couple of critical bugs:
* http://fiji.sc/bugzilla/show_bug.cgi?id=899
* http://fiji.sc/bugzilla/show_bug.cgi?id=908