Add type conversion utilities

gargantext/utils/convert.py

+def to_int(x, default=0):
+    try:
+        return int(x)
+    except (ValueError, TypeError):
+        return default
+
+
+def to_bool(x):
+    return not (
+        x is None or isinstance(x, str) and (not x or x.lower() == 'false'))
+
+
+def to_str(x):
+    if isinstance(x, str):
+        return x
+    return str(x)