Introduced data value object

Created by: stefanoborini

Replaced previous system of Result and Parameter objects for MCO, DataSource and KPICalculator with a set of DataValue objects that contain all the relevant information for a specific entity created by the MCO/DS/KPI

doc/source/api/force_bdss.core.rst

+force_bdss.core package
+=======================
+
+Subpackages
+-----------
+
+.. toctree::
+
+    force_bdss.core.tests
+
+Submodules
+----------
+
+force_bdss.core.data_value module
+---------------------------------
+
+.. automodule:: force_bdss.core.data_value
+    :members:
+    :undoc-members:
+    :show-inheritance:
+
+
+Module contents
+---------------
+
+.. automodule:: force_bdss.core
+    :members:
+    :undoc-members:
+    :show-inheritance: