revamped FileFilterExt

the "Open File" dialog was too annoying for me.
I pimped FileFilterExt to be more convenient and especially do no longer force the user to select the filetype in the dialog
BEFORE picking a file.

Change-Id: I6be4e8b02bb382c9906ac9f033f2633cd35a40fa
cleanup

Change-Id: I72ae95ccea0916e1863b6669cb095539502b047b
corrected .Matches() function

Change-Id: Ie7ff9061c0d9ff4cc790fc57fd802fc963c31097
file open/save dialog now features a combined pattern which subsumes all supported file types.

the user no longer has to first choose the file type in the bottom right.

another advantage:
the file/open code has been dramatically simplified and beautified.

Change-Id: I13000ad3643ac562bca1f084b5972bdbc06e5368