Move ThreadProxy template to util.h
remove legacy code
move asynchronous uploading from IoDispatcher to AbstractUploader
documentation of AbstractUploader
remove invalid assertion
adapt FileProcessor unittest
TEST: unit test for ThreadProxy template
make sure the writer thread is properly joined un AbstractUploader
remove TearDown() method (unused)
FIX: memory leak (non-virtual destructor in UploadStreamHandle)
TEST: unit test for AbstractUploader functionality
add worker thread to local uploader
use SynchronizingCounter for AbstractUploader
adapt unit tests of AbstractUploader
TEST: add unit test for basic buffer ordering
clearify callback_t in UploadStreamHandle
FIX: duplicate symbol leading to linker quirks
FIX: minor code smells
FIX: deadlock in local file upload