Misc. typos: Please merge right before 0.17 release

I'm still finding typos in the source code. I propose that you keep this PR open prior ro relaese and then merge  so that if I find other typos in the meantime they will be part this release.

src/App/Document.h

@@ -276,7 +276,7 @@ public:
     void setUndoMode(int iMode);
     /// switch the level of Undo/Redo
     int getUndoMode(void) const;
-    /// switch the tranaction mode
+    /// switch the transaction mode
     void setTransactionMode(int iMode);
     /// Open a new command Undo/Redo, an UTF-8 name can be specified
     void openTransaction(const char* name=0);

src/App/PropertyContainer.cpp

@@ -48,7 +48,7 @@ TYPESYSTEM_SOURCE(App::PropertyContainer,Base::Persistence);
 //**************************************************************************
 // Construction/Destruction
 
-// here the implemataion! description should take place in the header file!
+// Here's the implementation! Description should take place in the header file!
 PropertyContainer::PropertyContainer()
 {
     propertyData.parentPropertyData = 0;