make Persistent=true smarter

this (partially) fix this self-reported issue: https://github.com/systemd-cron/systemd-cron/issues/14

I hope this python code is not too awfull

For anacrontab , **AccuracySec=** should maybe be replaced by **OnBootSec=** !?

AccuracySec would be usefull to randomize monthly/weekly/daily jobs.
To avoid excessive backslashes, you can use parenthesis instead. Also, I would prefer `'p' not in job` instead of `not 'p' in job`, though it's more of personal preference, but it just sounds a little more human to me.

```python
if ('p' not in job and
       job['M'] == ['*'] and
       job['w'] == ['*'] and
       job['d'] == ['*'] and
       job['h'] == ['*']):
```