added a method to print debug backtrace
moved w() and backtrace() to class tx_newspaper_Debug [#1636]
added null values to [g|s]et{Start,End}time to differentiate unset times from value 0 [#1636]
pass changed values to dependency tree so that the tree can set correct start- and endtimes [#1636]
added kdevelop files and doxygen generated documentation to .gitignore