Added IEND chunk to end of generated PNG image.
Merge pull request #58 from sintefmath/cdyk_iss57

Added IEND chunk to end of generated PNG image.
Requiring cmake 2.6 and newer from now on.
Properly ran constructor of templated superclass (was missing template argument)
CMAKE: Altered some if-tests to use variable names without $\{\} as cmake 2.6 seems to like that better
Qt::MiddleButton replaced with Qt::MidButton as the former isn't supported on Qt-4.6
Refactored local enums to top of file in anonyomous namespace. Local types cannot be used as template arguments, but they were used in a std::vector
Removed a leftover $\{\} in an if-statement within cmakelist
Merge pull request #66 from sintefmath/kjetilly_rhel_fixing

Fixes needed for RHEL compatibility
merged master into feature branch and resolved conflicts
Removed screen number from offscreengl constructor (shouldn't be needed
with a proper display string), as well failing on empty display strings.
Began adding log callback support to reduce the std::cerr pollution.
Allows any logging system to be used.