Capitalize beginning of tooltips + Typos

Capitalized all remaining uncapitalized tooltips. 
+ Fixed typo in instantiate() function. Shouldn't have any repercussions on the code, AFAICT. 
+ other typos

src/Mod/Mesh/Gui/ViewProvider.cpp

@@ -332,7 +332,7 @@ ViewProviderMesh::~ViewProviderMesh()
 
 void ViewProviderMesh::onChanged(const App::Property* prop)
 {
-    // we gonna change the number of colors to one
+    // we're going to change the number of colors to one
     if (prop == &ShapeColor || prop == &ShapeMaterial) {
         pcMatBinding->value = SoMaterialBinding::OVERALL;
     }