Backport PR
#2102: Fix logging on interactive shell....
Backport PR
#2102: Fix logging on interactive shell.
Add a missing string format code in init_logs() and move init_logstart() after init_magics(), to fix dependency issues.
This is a proposed fix for the case a log file is given in `ipython_config.py`, eg:
```python
# Start logging to the given file in append mode.
import os
from time import strftime
f = os.path.join(c.TerminalIPythonApp.ipython_dir, strftime('%Y-%m-%d')+".py")
c.TerminalInteractiveShell.logappend = f
```
which completely breaks in current `master` code
