[core] change Attributes declaration on Node description

Inputs and outputs Attributes are now declared in two separate lists
* no more isOutput field on Attribute description
* guarantee attributes order (was not the case in Python2 with class attributes)
* Attribute's name is now part of its description

Note: for now, input and output Attributes are still stored in a single model inside a Graph.

meshroom/nodes/aliceVision/Meshing.py

@@ -6,10 +6,12 @@ class Meshing(desc.CommandLineNode):
     cpu = desc.Level.INTENSIVE
     ram = desc.Level.INTENSIVE
 
-    mvsConfig = desc.File(
+    inputs = [
+        desc.File(
+            name="ini",
             label='MVS Configuration file',
             description='',
             value='',
             uid=[0],
-            isOutput=False,
-            )
+            ),
+    ]