Move definition of std_grp to std.replicode

[jefft0]

user.classes.replicode loads std.replicode which defines groups like primary. These are defined in std.replicode like this using std_grp:

primary:(std_grp 2 0 0.4 0 |[])

Even though std_grp is used in std.replicode, the !def for it is in user.classes.replicode. This works because Replicode first runs a preprocessor on all the !def, then uses them. So it is possible for a !def to appear after it is used. But this is counter-intuitive. This pull request moves the !def for std_grp from user.classes.replicode to std.replicode.