Fix/core save api (#172)

* Acknowledge messaages from Pulsar, doh!
* Change API to deliver a boolean e if value is an entity
* Change loaders to use new API
* Changes, entity-aware API is complete

trustgraph-base/trustgraph/knowledge/__init__.py

@@ -1,4 +1,5 @@
 
+from . defs import *
 from . identifier import *
 from . publication import *
 from . document import *

trustgraph-base/trustgraph/knowledge/defs.py

@@ -23,3 +23,11 @@ URL = 'https://schema.org/url'
 IDENTIFIER = 'https://schema.org/identifier'
 KEYWORD = 'https://schema.org/keywords'
 
+class Uri(str):
+    def is_uri(self): return True
+    def is_literal(self): return False
+
+class Literal(str):
+    def is_uri(self): return False
+    def is_literal(self): return True
+

trustgraph-base/trustgraph/knowledge/document.py

@@ -1,6 +1,16 @@
 
 from . defs import *
-from .. schema import Triple, Value
+
+def Value(value, is_uri):
+    if is_uri:
+        return Uri(value)
+    else:
+        return Literal(value)
+
+def Triple(s, p, o):
+    return {
+        "s": s, "p": p, "o": o,
+    }
 
 class DigitalDocument:
 

trustgraph-base/trustgraph/knowledge/organization.py

@@ -1,6 +1,16 @@
 
 from . defs import *
-from .. schema import Triple, Value
+
+def Value(value, is_uri):
+    if is_uri:
+        return Uri(value)
+    else:
+        return Literal(value)
+
+def Triple(s, p, o):
+    return {
+        "s": s, "p": p, "o": o,
+    }
 
 class Organization:
     def __init__(self, id, name=None, description=None):

trustgraph-base/trustgraph/knowledge/publication.py

@@ -1,6 +1,16 @@
 
 from . defs import *
-from .. schema import Triple, Value
+
+def Value(value, is_uri):
+    if is_uri:
+        return Uri(value)
+    else:
+        return Literal(value)
+
+def Triple(s, p, o):
+    return {
+        "s": s, "p": p, "o": o,
+    }
 
 class PublicationEvent:
     def __init__(