fix for possibly invalid core calculation
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
Remove some old files
Merge pull request #274 from bastih/master

Mini fixes and cleanups
Fix namespaces in storage
Cleanup namespace transition in io
Cleanup access after namespace transition
Cleanup net after namespace transition
Merge pull request #275 from bastih/master

Namespace usage cleanups
Dynamic Parallelization.
Merge pull request #269 from kaihowl/pullrequest/kh-dynamic

Dynamic Parallelization.
Add optional extensions dependency
Performance and other improvements:
- Index based joins
- Renaming of columns in PC
- Performance Improvements
Merge pull request #271 from hyrise/feature/thrift

Index Based Operations
Local Storage for Queries for better usability
Introduce lazy sessions

Session contexts are only created when requests actually change data,
instead of creating contexts whenever a session starts.