BuildingSmart IFCRail changes to BIMTester (#1309)

* Add a way to validate the IFC file in BIMTester

* Fix an issue in Report where only the first error was shown

* Fix the usage of Schema in BIMTester

* Add Aggreation steps to BIMTester

src/ifcbimtester/bimtester/table.py

@@ -0,0 +1,19 @@
+from collections import defaultdict
+
+
+class TableModel:
+    """This class represents a table of data"""
+
+    def __init__(self, key_name=None, value_name=None):
+        self.rows = defaultdict(list)
+        self.key_name = key_name
+        self.value_name = value_name
+
+    def add_row(self, related, relating):
+        self.rows[related].append(relating)
+
+    def get_count(self):
+        return len(self.rows)
+
+    def get_count_distinct_values(self):
+        return len(set(item for sublist in self.rows.values() for item in sublist))