Cast weight vector to same datatype as spikes

Previously, attachData() did not check that the weight vector `w` was the same
datatype as the given spikes `Y`, which could cause an error when performing
model operations later. This was particularly annoying when accepting the
default value of `w`. This commit makes attachData() automatically cast `w` to
the same datatype as `Y`.

@MoDT/attachData.m

@@ -59,6 +59,9 @@ function attachData(self, Y_, t_, varargin)
 assert(ismember(datatype_,{'single','double'}), self.badValueErrId, ...
     'Datatype must be single- or double-precision floating point');
 
+% Cast w to the same datatype as Y
+w_ = cast(w_, datatype_);
+
 % (2) Assign values ------------------------------------------------------------
 
 % Clear caches