Add expression registration facility

* Add registration facility for custom AbstractExpressions
* Rework SpecialExpression to ExampleExpression
* Add example documentation
Merge pull request #13 from bastih/feature/tablescan_improvements

Add ability to create custom expressions

* Add registration facility for custom AbstractExpressions
* Rework SpecialExpression to ExampleExpression
* Add example documentation
This tests a server start
Merge pull request #17 from bastih/feature/test_server_start

Finally test an actual start of the server and assure existence of both /query/ and /urls/.
Introduce new base class for storables
Add abstract resource type forward declaration
Merge pull request #15 from lordgeorg/master

Adds table name display to difference table test output
Changes the behavior for the PlanOperation::distribute() method

Now the out paramers will be start and end with end be one after
the acutal element so it can be used as in traditional while x < end
comparisons
Merge pull request #22 from hyrise/feature/table_partitioning

Changes the behavior for the PlanOperation::distribute() method
Clean up HashTable constness and some related issues
Merge pull request #23 from bastih/feature/cleanup_hashtable_constness

Clean up HashTable constness and some related issues
Improve getAttributeVector non-implemented exception
changed hyrise server to not shut down with execption if hwloc_set_membind is not supported
Fixing visibility of queue type in WSSimpleTaskScheduler
Fixing bug in Histogram calculation for Non Row Containers
optimized RadixJoin for PointerCalculator
Merge remote-tracking branch 'upstream/feature/radix_join' into feature/radix_join
Fixed interface of virtual RadixJoin Operator to accept two fields as input
Adding Dot Product Plan Operation
HYRISE as a Web Server

This commits adds basic functionality to query the HYRISE server via a simple web interface.
This is achieved by adding a static request handler that will simply return static files
from the file system. To build the correct mime type for the response it uses the mime type
list from the Apache Server project and parses this at startup time. The static FS path
can be set via the environment variable HYRISE_STATIC_PATH or defaults to the current
working directory + static, e.g. something like `cwd`/static

As a first consumer this commit adds the web query interface that allows to run queries
directly from the browser using JavaScript. The result will then be rendered as a classical
table.