[EPIC] Internal format

[Svetlana-Asinovskaia]

Acceptance criteria:

1. Internal ketcher format contains (load and save) information about highlighted atoms and bonds
2. Ket format supports CIP labels for atoms. CIP labels are moved from S-groups to Atom properties.
3. If user saves a structure with data s-group the bonds information is saved into "bonds" property (specification is updated). The "bonds" array contains selected bonds indices.
4. The internal .ket format is used while using the server functions in order to support the transfer of additional metadata.
5. If user adds multiple reaction arrows (reaction equilibrium arrows) to the canvas they are displayed correctly after saving in .svg format.
6. Simple objects (drawn with 'Shape Ellipse', 'Shape Rectangle', 'Shape Line' tools), text objects, reaction equilibrium arrow and multiple arrows are not removed from the canvas after calling the server functions.