export: old files not removed from docroot

[erwin]

If a page is removed, its exported file isn't removed from the export dir.

Removing all html files before copying to new ones is probably not an option since it would cause the site to be broken for a couple of seconds.

[joeri]

The removal of the exported files should be done in the following cases:

• a page is removed
• a page is being archived
• a page is being unpublished

[erwin]

this can be fixed by rsyncing the exported html files with the docroot. (with --delete option)

to make sure removed/archived pages are removed, an export notification has to be built in. see #138

CAUTION: using the --delete option will cause all manually copied files to be removed (if any) also the /stats directory would be removed, so an exception has to be built in for that

[erwin]

fixed in build 38

DEPLOYMENT REQUIREMENTS (for projects that use exports):

• create a link from /var/projects/PROJECT/pictures to /var/projects/PROJECT/files
• create an exclude file in the export dir of the project containing the files or directory that should be excluded. by default an exclude file is created containing 'stats'