Added ignoring of abstract methods

Abstract methods are not interesting in dead code
analysis as they can not be called by design.
Merge pull request #32 from soxofaan/ignore-abstract-methods

Ignore abstract methods
(Re)introduce progress bar

A progress bar was originally implemented with ezcConsoleProgressbar,
but this was removed by commit 31d5d775f8bedb6a189ed8289047c3d87b04e7e4

This commit re-introduces a progress bar using Symfony\Component\Console\Helper\ProgressHelper
Made the progress bar optional (disabled by default) with option --progress