public void setEntries(final List<VariableEntry> vars) {
        clear();
        for (VariableEntry entry : vars) {
            if (this.variablesSet.containsKey(entry.varname)) {
                //must be a database error, ignore duplicate variable
                continue;
            }
            variableMap.put(entry.varname, entry.formula);
            this.variableList.add(entry.varname);
            this.variablesSet.put(entry.varname, entry.id);
        }
        wasModified = false;
    }
Tidies up this variable list. This means doing the following things:
* remove empty entries without dependency of any other var (or from varsToKeep list)
* add empty entries for all missing vars
* sorts vars alphabetically
main/src/main/java/cgeo/geocaching/utils/formulas/VariableList.java