Remove unused import
Fix off by one error

+ regression test and a small fix to avoid comparison errors
Clean up unicode handling

Now, all text input gets immediately converted to unicode
and everything is used in unicode versions.
Since the old bulkmodify adapters weren't explicit in
wether they work with unicode or string objects, I made
it explicit and adapters now must implement access with
both unicode and utf-8 encoded versions of the same text
the code ended up only using the utf-8 version.
When you look veery closely at the previous version of this
code you might be able to spot that I did offset calculations
looking at the length difference between an unicode object
and an utf-8 encoded string. This creates havoc as soon as
you use non ascii chars. I added a regression test for it.
If you want to see what I mean, modify rt/bulkmodify/browser/view.py:115
so that one of the two variables gets utf-8 encoded and you
will trigger the failure in the new regression test.