Zucchi/filter tweaks

[zucchi]

I have had to update the Decompress filter by changing the __invoke() method to filter() to match the API of the Compress filter and make it functional when used with the File Transfer component

I have also updated the the Tar Adapter as it was failing to interact properly with the "Archive_Tar" pear library causing it to fail. This included adding a lambda callback to handle PEAR errors. This doesn't however catch issues in the constructor.

[weierophinney]

Removing __invoke() is a BC break, even if it was not correctly named. Reintroduce __invoke()``and have it proxy tofilter()`.