* trac/util/text.py for the unicode and text formatting utilities
* trac/util/datefmt.py for the date formatting and parsing utilities
* reorganized a bit the remaining functions in __init__.py
1. algorithmic functions
2. os/sys utilities
3. crypto utilities
* adapted all the `import` statements for the above changes
* fixed a few remaining !TracError import from `trac.util`
(should be from `trac.core`).