Load correctly split views and refactor

Commit 94feeeec started loading views differently depending on whether they belonged or not to the tab container. However, it only checked whether a view's parent was the tab container, which didn't take into account split views. A split view has a container as parent, but it is still inside the tab bar: this caused the view not to be loaded correctly. This merge request fixes the issue by checking whether any of a view parents is the tab bar.

It also attempts to make the loading code a bit more readable by splitting KonqViewManager::loadItem in several functions depending on the type of item to load.