render : store dependencies

[vincent-peugnet]

When a page is rendered, store in a metadata the IDs of pages that where used to render this one (templates, rss, lists).

When a page is read, in addition to compare datemodif with actual date, compare all dependencies pages as well. If a dependency page has been edited later than the page itself, this will cause a re-rendering.

This should be very better by using file-system modification date instead of reading and parsing the json Page.

• [ ] store page dependency
• [ ] store not yet existing page dependency
• [ ] store bookmark dependency
• [ ] check for date modif when page read
• [ ] add an option in config file
• [ ] use file system modification instead of parsing page