Resurrect tests for columnfile.py, correct np.int

In the Github Actions CI, the command "python -m pytest" is run to test ImageD11.
By default, this only runs test files with the naming convention `test_*.py`
Renamed `testcolumnfile.py` to `test_columnfile.py` to fix this.
Also, replaced `np.int` references `int` to fix numpy depreciation errors.

ImageD11/columnfile.py

@@ -212,7 +212,7 @@ def removerows( self, column_name, values, tol = 0 ):
         """
         col = self.getcolumn( column_name )
         if tol <= 0: # integer comparisons
-            col = col.astype( np.int )
+            col = col.astype( int )
             mskfun = lambda x, val, t: x == val
         else:        # floating point
             mskfun = lambda x, val, t: np.abs( x - val ) < t
@@ -502,7 +502,7 @@ def colfile_to_hdf( colfile, hdffile, name=None, compression=None,
         g.attrs['ImageD11_type'] = 'peaks'
         for t in c.titles:
             if t in INTS:
-                ty = np.int64
+                ty = int64
             else:
                 ty = np.float64
             # print "adding",t,ty
@@ -534,7 +534,7 @@ def colfileobj_to_hdf( cf, hdffile, name=None):
         g.attrs['ImageD11_type'] = 'peaks'
         for t in cf.titles:
             if t in INTS:
-                ty = np.int64
+                ty = int64
             else:
                 ty = np.float64
             g.create_dataset( t, data = getattr(cf, t).astype( ty ) )