relax SVN archive

The command used was:
svn cp svn+ssh://bugman@.../svn/relax/1.3 svn+ssh://bugman@.../svn/relax/branches/spin_loop_bool

The spin_loop and its siblings cannot currently handle the branching tree formed by the Selection
object (nested within Selection._union and Selection._intersect). For example if there are two
molecules loaded into the data store, 'Ap4Aase' and 'RNA', the spin_loop with the spin id string
'#Ap4Aase:Glu | #RNA@...' loops over all spins of both molecules!!! Therefore all the usages of the
Selection object need to be redesigned, and possibly the Selection object itself.