Fix enumeration of GlobbalPlatformISDR during card_init()

We used __subclasses__(), but this only returns the immediate
subclasses and not all further/nested subclasses.  Instead, we must
use the pySim.utils.all_subclasses() function to really get all of them.

The hack to use the method signature of the constructor to determine if
it's an intermediate class didn't work, as even GlobbalPlatformISDR
has a optional argument for non-default AIDs.  So let's introduce an
explicit class attribute for that purpose.

Change-Id: I7fb1637f8f7a149b536c4d77dac92736c526aa6c
diff --git a/pySim/global_platform.py b/pySim/global_platform.py
index 2ed6ee4..0ceb884 100644
--- a/pySim/global_platform.py
+++ b/pySim/global_platform.py
@@ -267,6 +267,7 @@
 
 # Card Application of a Security Domain
 class CardApplicationSD(CardApplication):
+    __intermediate = True
     def __init__(self, aid: str, name: str, desc: str):
         super().__init__(name, adf=ADF_SD(aid, name, desc), sw=sw_table)