Misc. typos and whitespace

Found via `codespell -q 3 --skip="*.po,*.ts,./.git,./src/3rdParty,./src/CXX,./src/zipios++,./src/Mod/Assembly/App/opendcm,./ChangeLog.txt" -I ../fc-word-whitelist.txt` and `grep`. Excess whitespace auto-removed by Atom editor.

src/Base/UnitsSchemaInternal.cpp

@@ -94,7 +94,7 @@ QString UnitsSchemaInternal::schemaTranslate(const Quantity &quant, double &fact
         factor = 1.0;
     }
     else if (unit == Unit::Mass) {
-        // TODO Cascade for the wights
+        // TODO Cascade for the weights
         // default action for all cases without special treatment:
         unitString = quant.getUnit().getString();
         factor = 1.0;