BUG: Fix ctkAppLauncherConfigure dependencies

Change rule to generate the launcher configuration to actually depend on
the input files (i.e. the scripts that contain the configuration files).
This fixes failure to regenerate the configuration when changes are made
at the CMake level.

Also, add some comments and fix the script dependency for generating the
configurations, which should be the script we invoke to do so, not the
script which contains the macro to create the target (which is in no way
useful as a dependency; at least not with the new, correct
dependencies).

Note that this is a little (but harmlessly) over-zealous right now, as
it forces regenerating the configuration any time the project is
reconfigured (as the input settings files are currently being written
unconditionally). This is addressed by f64df2a0f515 in a separate
branch, where writing the settings files is changed to only update the
files if the contents would change.
BUG: "Fix" creation of launcher executable

Remove rule in ctkAppLauncher-configure.cmake to create the launcher
executable in favor of a build rule set up by ctkAppLauncher.cmake. This
reduces dependency twining, and the dependencies should now be correct
to update the executable if the source instance changes or if it has
been deleted, without the launcher configuration also needing to be
regenerated.
Merge pull request #42 from mwoehlke-kitware/dependency-fixes

Dependency fixes

Tested on Ubuntu 13.10 on Debug build against the Slicer `launcher-improvements` topic. Configuration, build and packaging of Slicer works well.