Implement support for SQLite blob to bytea, fixes #59.

This issue has been re-opened with blob instead of double. Semi-blindly
implement support for the blob type with an image data type.

Disturbingly enough when tested with non-binary data SQLite was
returning strings rather than byte vectors, tripping up the transform
function that sure expects byte vectors.

src/sources/sqlite.lisp

@@ -20,8 +20,8 @@
 	      (string-equal sqlite-type-name "nvarchar" :end1 8)) "text")
 
 	((string-equal sqlite-type-name "datetime") "timestamptz")
-
-        ((string-equal sqlite-type-name "double") "double precision")
+        ((string-equal sqlite-type-name "double")   "double precision")
+        ((string-equal sqlite-type-name "blob")     "bytea")
 
 	(t sqlite-type-name)))
 
@@ -138,6 +138,9 @@
 			   ((string-equal "text" coltype)
 			    nil)
 
+                           ((string-equal "bytea" coltype)
+                            #'pgloader.transforms::byte-vector-to-bytea)
+
 			   (t
 			    (compile nil (lambda (c)
 					   (when c