handlers/dup: make use of new lib/vserver functionality

lib/vserver.in [init_vservers] : canonicalize VROOTDIR (since duplicity et al. don't follow symlinks)

 If vservers weren't enabled it was impossible to enter the src
 menu in ninjahelper due to how these functions returned. This sets
 the variable host_or_vserver='host' when vservers are not available
 and then returns with a nice exit code

 ninjahelper: moved (and enhanced) vservers-related functions to lib/vservers. dup.helper, pgsql.helper: use these functions

 Moved more code to lib/ (conffile-related functions, parseini. Added dup helper, using new modular vservers-related functions shared for all helpers.

 Autotools: when cleaning, delete generated files in lib dir.

 Start to move common functions (maketemp) to lib/tools, and better use autotools for lib/{easydialog,tools}.

 Moved easydialog.sh to lib/ directory: more code is going to be shared, let's start here.