changelog cosmetics

 pgsql.helper: forbid the user to choose an empty database set to backup

 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.

 Fix: the "Cancel" buttons used to have a weird behaviour... at least

 Fix ChangeLog entry.

 Fix: used to expand '*' in default source directories

Also fixed a bug in the rdiff handler that caused a unary operation error if
the variable wasn't fixed