BaseTools: Workspace classes refactor properties

1) use decorators
2) also change some private functions to public when all callers are
external
3) change external callers to use functions instead of directly
accessing private data.

Cc: Liming Gao <liming.gao@intel.com>
Cc: Yonghong Zhu <yonghong.zhu@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Jaben Carsey <jaben.carsey@intel.com>
Reviewed-by: Yonghong Zhu <yonghong.zhu@intel.com>

BaseTools/Source/Python/Workspace/WorkspaceDatabase.py

@@ -302,25 +302,21 @@ determine whether database file is out of date!\n")
         return PackageList
 
     ## Summarize all platforms in the database
-    def _GetPlatformList(self):
-        PlatformList = []
+    def PlatformList(self):
+        RetVal = []
         for PlatformFile in self.TblFile.GetFileList(MODEL_FILE_DSC):
             try:
-                Platform = self.BuildObject[PathClass(PlatformFile), TAB_COMMON]
+                RetVal.append(self.BuildObject[PathClass(PlatformFile), TAB_COMMON])
             except:
-                Platform = None
-            if Platform is not None:
-                PlatformList.append(Platform)
-        return PlatformList
+                pass
+        return RetVal
 
-    def _MapPlatform(self, Dscfile):
+    def MapPlatform(self, Dscfile):
         Platform = self.BuildObject[PathClass(Dscfile), TAB_COMMON]
         if Platform is None:
             EdkLogger.error('build', PARSER_ERROR, "Failed to parser DSC file: %s" % Dscfile)
         return Platform
 
-    PlatformList = property(_GetPlatformList)
-
 ##
 #
 # This acts like the main() function for the script, unless it is 'import'ed into another