Squashed 'lib/' changes from f19fb40..2fa268c

2fa268c #38 Bugs are fixed
9140aac #38 Refactoring
ee685e4 #56 Small changes
f61eeea #38 mapping for handles of graphics objects
b0e041f Issue #56 Enhanced test coverage
646942b Issue #56 Bug fixes
6450301 Issue 56
cddc939 Issue 56 A few bug fixes
4c8d175 Issue 56 In progress

git-subtree-dir: lib
git-subtree-split: 2fa268cf8ea0436f69a34f1bb3f169849d3f5c33
Merge commit '9d3076dea9d92daf71395f7723b60c4d0f395024' into ellmaster