restructuration of the documentation

doc/source/containers.rst

@@ -0,0 +1,29 @@
+===============
+Container types
+===============
+
+Containers allow to manage collection of values of homogeneous type.
+Three container types exist.
+
+A container is a non-mutable structure once it has been locked.
+Consequently just insert procedure are needed
+
+Lists
+-----
+
+Correspond to an ordered list of values belonging an elementary type.
+
+At its creation
+
+
+Sets
+----
+
+Correspond to an unordered set of values belonging an elementary type.
+
+
+Dictionaries
+------------
+
+Dictionaries allow to associate a `key` to a `value`. Values can be retrieved through its associated key.
+Values must belong an elementary type and keys must be *OBIStr_t*.