Implemented fixes for bug 170

Implemented fixes for bug 170
1. Circ2::returnbook will throw an exception if $branch is undef
2. branch/printer-getting code is modularized into getbranch and getprinter
   with correct logic from circulation.pl (temporarily put into Circ2.pm)
3. circulation.pl and returns.pl modified to use above functions

Noted correct tab sizes for the files; returns.pl partially reformatted to
conform to the dominant correct tab size

Handle non-latin1 charsets for returns.pl