filesystem: Use Tuple for transparent file size

As the documentation strings say: The size should be a *tuple*.  In
reality we so far passed a set.  The problem with the set is that
ordering is not guaranteed, and hence we cannot assume the first and
second item have meaning (minimum vs. default size).

While at it, use a type annotation to catch such bugs easily.

Change-Id: I553616f8c6c4aaa8f635b3d7d94e8e8f49ed5a56
diff --git a/pySim/ts_31_102_telecom.py b/pySim/ts_31_102_telecom.py
index c020a07..06317b9 100644
--- a/pySim/ts_31_102_telecom.py
+++ b/pySim/ts_31_102_telecom.py
@@ -234,7 +234,7 @@
 
 # TS 31.102 Section 4.6.4.1
 class EF_MST(EF_UServiceTable):
-    def __init__(self, fid='4F01', sfid=0x01, name='EF.MST', desc='MCS Service Table', size={2,2},
+    def __init__(self, fid='4F01', sfid=0x01, name='EF.MST', desc='MCS Service Table', size=(2,2),
                  table=EF_MST_map, **kwargs):
         super().__init__(fid=fid, sfid=sfid, name=name, desc=desc, size=size, table=table)
 
@@ -265,7 +265,7 @@
 
 # TS 31.102 Section 4.6.5.2
 class EF_VST(EF_UServiceTable):
-    def __init__(self, fid='4F01', sfid=0x01, name='EF.VST', desc='V2X Service Table', size={2,2},
+    def __init__(self, fid='4F01', sfid=0x01, name='EF.VST', desc='V2X Service Table', size=(2,2),
                  table=EF_VST_map, **kwargs):
         super().__init__(fid=fid, sfid=sfid, name=name, desc=desc, size=size, table=table)