change behaviour of instrument assignment

instrument assignment is persistent
if a stream has to be unassigned from a stream, assign it
to the dummy instrument '0'

t.py

@@ -17,11 +17,9 @@ crv([start], [stop], [mod.par], ['float'], [interval=...,] [add_prev=False,] [ad
 
 now = int(time.time())
 result = {}
-maxcurves = 7
-maxpoints = 7
 
 
-def prt():
+def prt(maxpoints=7, maxcurves=7):
     for i, (key, curve) in enumerate(result.items()):
         if i > maxcurves:
             print('--- ...')
@@ -40,21 +38,20 @@ def prt():
                     print(fmtime(row[0]), row[1:])
 
 
-def qry(*args, **kwds):
+def qry(*args, maxpoints=7, maxcurves=7, **kwds):
     result.clear()
     result.update(db.query(*args, **kwds))
-    print('PRINT')
-    prt()
+    prt(maxpoints, maxcurves)
 
 
-def crv(*args, **kwds):
+def crv(*args, maxpoints=7, maxcurves=7, **kwds):
     result.clear()
     res = db.curves(*args, **kwds)
     if isinstance(res, list):
         result[()] = res
     else:
         result.update(res)
-    prt()
+    prt(maxpoints, maxcurves)
 
 
 def sry(prectime=False):