Migration updates

For the following issues:
- [MAGN-3336](http://adsk-oss.myjetbrains.com/youtrack/issue/MAGN-3336) Incorrect migration for Average XYZ
- [MAGN-3263](http://adsk-oss.myjetbrains.com/youtrack/issue/MAGN-3263) Number to string should migrate to String.FromObject
- [MAGN-3262](http://adsk-oss.myjetbrains.com/youtrack/issue/MAGN-3262) Selection info is not retained after migration for (Select Face, Select Edge, Select Point On Face)