Templatize loops in imgdiag

Now converted the code for analyzing and dumping a region to use a template
class that can be specialized for each content type.  I still have not
added the contents for ArtMethod.

Bug: 62554875
Test: adb shell imgdiag --image-diff-pid=<app pid> --boot-image=/system/framework/boot.art
Change-Id: I07cecadd566f67c0920039ea35ff7ca2a9951fac