Add more extensions to Resources source group by default

Extend the Resources group regex to match pdf, png, jpeg, jpg,
storyboards, and xcassets.  This cleans up more complex Xcode projects a
lot.

While at it, factor the regular expressions for both "Resources" and
"Source Files" into macros.

Source/cmMakefile.cxx

@@ -87,12 +87,10 @@ cmMakefile::cmMakefile(cmGlobalGenerator* globalGenerator,
 
 #if defined(CMAKE_BUILD_WITH_CMAKE)
   this->AddSourceGroup("", "^.*$");
-  this->AddSourceGroup("Source Files",
-                       "\\.(C|M|c|c\\+\\+|cc|cpp|cxx|f|f90|for|fpp"
-                       "|ftn|m|mm|rc|def|r|odl|idl|hpj|bat)$");
+  this->AddSourceGroup("Source Files", CM_SOURCE_REGEX);
   this->AddSourceGroup("Header Files", CM_HEADER_REGEX);
   this->AddSourceGroup("CMake Rules", "\\.rule$");
-  this->AddSourceGroup("Resources", "\\.plist$");
+  this->AddSourceGroup("Resources", CM_RESOURCE_REGEX);
   this->AddSourceGroup("Object Files", "\\.(lo|o|obj)$");
 
   this->ObjectLibrariesSourceGroupIndex = this->SourceGroups.size();

Source/cmSourceFile.h

@@ -120,4 +120,10 @@ private:
 // TODO: Factor out into platform information modules.
 #define CM_HEADER_REGEX "\\.(h|hh|h\\+\\+|hm|hpp|hxx|in|txx|inl)$"
 
+#define CM_SOURCE_REGEX                                                       \
+  "\\.(C|M|c|c\\+\\+|cc|cpp|cxx|f|f90|for|fpp|ftn|m|mm|rc|def|r|odl|idl|hpj"  \
+  "|bat)$"
+
+#define CM_RESOURCE_REGEX "\\.(pdf|plist|png|jpeg|jpg|storyboard|xcassets)$"
+
 #endif