Make several small string fixes in linearize-data.py

- Add a space after the fixed string prepended to file names when input or
  output file changes
- Clarify the error message when the genesis block is not found in the
  hash list (...why do we have this at all?)
Remove genesis block hash from error
Merge pull request #5440

ebdd6bf Remove genesis block hash from error (Micha)
8d174d6 Make several small string fixes in linearize-data.py (Micha)