mdbrebase: fix prefix replacement, add regex & filename modes

Existing prefix replacement was incorrect as
it tested for a prefix but performed a multi
search and replace instead of just a prefix
replace. Fix that.

Add -r|--regex mode to indicate that path
replacement should be performed with regular
expressions.

Add -f|--filename mode to indicate that
replacements should be performed only on
a file name and not the full absolute path.

Add -v|--verbose mode to print the replacements
that are performed.
Merge pull request #770 from abock/master

mdbrebase: fix prefix replacement, add regex & filename modes