Adds lots and lots of namespaces ... and some related things:

* more pragma once
* more auto (where namespaces would just have to been verbosely written)
* some lines removed (if obviously unnesessary and namespaces would have to be
   applyed)
* removed some now unnessesary namesapce references (mostly "hyrise::")
Fixed concurrency issue in InsertScan and PosUpdateScan:
Thread A: fetch before_size
Thread B: fetch before_size
B: append_to_delta
A: append_to_delta
For A, before_size+i is not the correct way to address its new rows anymore
Merge pull request #272 from lordgeorg/namespaces

More consequent namesapces in hyrise
Merge pull request #273 from hyrise/fix-insertscan-concurrency

Fixed concurrency issue in InsertScan and PosUpdateScan:
Prevent 'maybe uninitialized error' and improve error handling