Fix a number of crashes when views are destroyed.  Avoid deleting widgets explicitly where possible, using QObject parent-child mechanism instead.  Defer deletion using object->deleteLater() instead of 'delete object'.  Make filter chains own their filters and take responsibility for deleting them, instead of having other objects deleting filters without removing them from the chain.  Add API documentation to the filter classes.

svn path=/branches/work/konsole-split-view/; revision=624111