Merge pull request #324 from reneme/fix_unittest

FIX: Endless Loop due to Compiler Optimization
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
Add a SynchronizedCounter to util_concurrency
TEST: unit test for the SynchronizingCounter
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