Clean up tests after removing 3.x applications and couch_views updates

 * Update the couch_views include paths

 * Exclude non-existent applications from setup logic

 * Do not run tests agains the backdoor port

 * Do not run tests checking for non-existent system dbs

 * Since "new" couch_att attachment format has changed a bit and encoding is
   not `identity` and `md5` is not `<<>>` any longer, some tests had to be
   updated to set those explicitly.
22 files changed