Find available build configurations automatically.
Minor cleanup: sort and comment on external projects
Make ANN optional on superbuild level
Make Eigen library optional on superbuild level
Support internal and external module whitelists.
Merge branch 'bug-18532-ModuleAndPluginWhitelists' of mitk.org:MITK into bug-18532-ModuleAndPluginWhitelists
Support internal and external plugin whitelists.
Only evaluate app dependencies of enabled apps.
Made whitelist macros consistent.
Fixed mitkFunctionEnableModules/Plugins functions.
Set default plugins variable to empty string.
Refactored module and plugin whitelisting.
Wrote documentation.
Added paragraph about whitelist file format.
Merge branch 'bug-18532-ModuleAndPluginWhitelists'