start working on install target
some problems:
- a FreeBSD port should use INSTALL_DATA, INSTALL_SCRIPT,
  INSTALL_PROGRAM .. to have the permissions right,
  but zotonic has *a lot* of files (and questionable permissions
  in the src zip), this would lead to a large port Makefile
  and long plist, how should this be maintained, when zotonic
  has new releases?
- zotonic might expect to keep its relative directory layout,
  while FreeBSD's hier(7) would like to spread dirs differently,
  see the DOCSDIR for example