[JENKINS-17363] Ludicrously slow load time [with lazyloading]
[JENKINS-19437] Implement load on demand functionality in Cppcheck

- Lazy loaded details are stored in CppcheckResult member variable and never released by Java garbace collector since a reference to them exists forever. All build.xml files are loaded during Jenkins startup and never released, CppcheckResult objects are part of them. This is kind of a memory leak. The update will cause slight lower performance but releasing of the memory is much more important for long run tasks/daemons/servers.
- Method lazyLoadSourceContainer() updated to return the data instead of their caching in a member variable.
- If cached CppcheckSourceContainer object can't be loaded, an empty one will be created. Different constructor used to remove unnecessary exception catches. Recently added related if removed from CppcheckSourceContainer.
- Condition moved from index.jelly to summary.jelly to be able to reuse the data and remove one unnecessary loading (performance).
- Construction "key = ++key" has no meaning, updated to "++key" to resolve a warning.