Update dashboard driver script to submit a regular project layout.

As discussed during the CTK hackfest, instead of submitting submitting
each CTK libraries, plugins, applications as a separate CDash subproject.
This commit reverts to a "regular" CDash layout where the
configure/build/test results are all presented on a single page. This will
be easier to maintain and less confusing for the developer.

Finally, the driver script is now downloaded directly from Github. This is
now possible by using CMake version >= 2.8.9 having built-in support
for https download. See [1]

Fixes #457

[1] http://cmake.org/gitweb?p=cmake.git;a=commit;h=4bcd84e65ad2f792c549989b9d773191ad75e5eb
Remove configuration of unneeded Project.xml and CTestConfigSubProject.cmake

See #457
Merge branch '457-revert-to-regular-cdash-submission'

* 457-revert-to-regular-cdash-submission:
  Remove configuration of unneeded Project.xml and CTestConfigSubProject.cmake
  Update dashboard driver script to submit a regular project layout.
Do not include now nonexistent module ctkFunctionGenerateProjectXml
Merge branch '457-revert-to-regular-cdash-submission'

* 457-revert-to-regular-cdash-submission:
  Do not include now nonexistent module ctkFunctionGenerateProjectXml
Fix condition used to unset DICOMApplicationHosting top level option

The variable CTK_PLUGIN_org.commontk.dah.app has been changed
into CTK_PLUGIN_org.commontk.dah.hostedapp.
Ensure ctk option are considered as superbuild candidate variable.

This fix issue introduced following commit dc70d03 and extend
the functionality of the external project dependency module by
introducing the "_SKIPCACHEVALUE" option.

By setting the variable <varname>_SKIPCACHEVALUE, the system
won't consider the cached value of an option. This is currently needed
in CTK because enabling top level option set the variable in the
current scope without setting the variable in the cache. For that
matter, the value in the current scope should be considered.

Note that the upstream project [1] hosting the external project dependency
macro hasn't yet been updated to support the skip cache value variable.

[1] https://github.com/commontk/Artichoke
Merge branch 'fix-passing-of-option' into dah-stlouis2014