* Removed "using Base::operator=" from GenericMatrix<> and GenericVector<>. They caused build errors under MSVC. Compiler-generated operator= should be fine.
* Changed "or" and "and" to "||" and "&&" operators. Not all compilers understand "or" and "and".
* Added missing header <algorithm> to interval.ipp
* Fixed MSVC build error in vector.cpp
* Removed "using namespace std" in objective.cpp, which was causing another build error under MSVC.
Refactored symbolics API; beware leaking memory like crazy
Merged with mvukov/issue_111, did some small fixes -- now it compiles under MSVC!
MSVC build errors fixed
Added the updated interface to HPMPC
Making Hessian symmetric changed from warning to info.
If testing is ON, warnings are considered as a failure.
Merge branch 'master' of github.com:mvukov/acado into issue_111
Revert "Making Hessian symmetric changed from warning to info."

This reverts commit a6054deb8a07366f704612c0502e280b85addbde.
Fixing a6054de.
Merge branch 'master' of github.com:mvukov/acado into issue_111
Fixing the symbolics API, issue #111
Fixing the fourtankNMPC.cpp example
Fixing parameter_estimation_tutorial2.cpp example
Trying to fix the powerkite_on.cpp example
powerkite_on.cpp example fails, move it to dev
Fixing the fourtankNMPC.cpp example
Fixing parameter_estimation_tutorial2.cpp example
Trying to fix the powerkite_on.cpp example
powerkite_on.cpp example fails, move it to dev