Add admin command for scraping new item

[maciejmatczak]

• job should be run once every 24 hours - around time chosen by the user, but the command will be invoked every 5 (?) minutes
• optional random delay as command input
• new item should be added only when it is not yet registered (according to known facts - the same url should produce new item register if any of the gathered parameter is changed)
• new items should be highlighted as "new" - up to the moment when user views them
• command to be installed by cron

Task list:

• implement initial command which creates the new items on every active job on runtime (no delay yet)
• cover it with small tests
• add mechanism for running every 5 minutes, but invoking scraping when around specific hour
• cover with functional tests

[maciejmatczak]

Mechanism to run every 5 minutes
Job needs to be run in one of the 5 minutes window during a day, so:

• add new model field, daily_run; if set time is smaller then current time and the job was not yet run - execute it and change the status
• every 24 hours reset all jobs

Easy to implement. Can have issues around reset time. Maybe there are better ready solutions (preferably light) for cron like tasks?

[maciejmatczak]

Something more user friendly options would be better, like every 5 minutes, 1 hour, 24 hours, etc.