One more change in accessing items from Cursor
One more change in accessing items from Cursor

Accessing items through mut borrow caused a lot of pain in the code, so
instead the value is moved and can be unwrapped back later. This will
require one more line of code like `cursor = item.into_inner()`, which
shouldn't be a problem as cursor should be already mutable and previous
code required creating artificial block anyway.

Note, no documentation provided as the whole item access thing has to be
rewritten.

dropbox/lmdb-rs,frew/lmdb-rs,vhbit/lmdb-rs,vhbit/lmdb-rs,mneumann/lmdb-rs,dropbox/lmdb-rs,frew/lmdb-rs,tempbottle/lmdb-rs,tempbottle/lmdb-rs,mneumann/lmdb-rs