Olympus’ E-30 fills the hole in its dSLR lineup. (Credit: Olympus America) With a price gap of about $900 between the Olympus E-520 and the E-3, Olympus has long had a pretty big hole in its dSLR lineup--a hole populated by extremely popular competitors like the Nikon D90, the Canon EOS 40D, and the Canon EOS 50D. But with the announcement of the E-30, it looks like Olympus is entering...