Added examples, casestudies
Make row iterator return roe index instead of statement
Fix examples
Added a lot of documentation, notes and additionaly functions
Split up func.hpp/cpp

--HG--
rename : func.cpp => context.cpp
rename : func.hpp => context.hpp
rename : func.cpp => value.cpp
rename : func.hpp => value.hpp
Aggregation functions; config* functions, misc global functions

--HG--
rename : detail.hpp => error.hpp
Aggregate cleanup, more aggregate tests
Moved initial value parameter for aggregates to front
Removed legacy imports
Cleaned up aggregate/function handling
Renamed func.[ch]pp to function[ch]pp

--HG--
rename : func.cpp => function.cpp
rename : func.hpp => function.hpp