Add core filename to output of fusesoc core show.

This commit updates the output of `fusesoc core show` to add the
filename of the core file itself. This change is required for tools such
as the filelist Edalize backend as discussed in
olofk/edalize#25.

The output of `fusesoc core show` now looks like:

CORE INFO
Name:        vee:el:en:vee
Description: Top bombing
Core root:   /root/path/to/core/file
Core file:   basename.core

fusesoc/capi2/core.py

@@ -33,8 +33,7 @@ def __init__(
 
         self.cache_root = cache_root
 
-        basename = os.path.basename(self.core_file)
-
+        self.core_basename = os.path.basename(self.core_file)
         self.core_root = os.path.dirname(self.core_file)
 
         # Populated by CoreDB._solve(). TODO: Find a better solution for that.
@@ -516,6 +515,7 @@ def info(self):
 Name:        {}
 Description: {}
 Core root:   {}
+Core file:   {}
 
 Targets:
 {}"""
@@ -539,6 +539,7 @@ def info(self):
             str(self.name),
             str(self.get_description() or "<No description>"),
             str(self.core_root),
+            str(self.core_basename),
             targets,
         )