Introduced struct DebuggerStartParameters to pass around
start parameters, removing the need for the engines to
access private members of DebuggerManager. Pass it
to DebuggerManager::startNewDebugger() and move
the GUI parts of that function into DebuggerPlugin,
making it possible to create the struct from command line
parameters. Introduce command line parsing with a few more
-enable-xx options. Introduce warning() to debugger panel
in the CDB engine.

On this occasion, clean out a few trailing whitespaces.