Fixed character region parsing in FontDescription

First off, the default ASCII characters were always included.

Second, the CharacterRegion was ignored due to incorrect deserialization.
Example:
```
      <CharacterRegion>
        <Start>32</Start>
        <End>127</End>
      </CharacterRegion>
```
This was deserialized as "add characters from `3` to `1`, which added nothing.

Thanks to these two mistakes the character region was always 32-126.