Support parsing KET file for macromolecules on ketcher side

[rrodionov91]

Requirements

It needs to render monomers and connections from KET file. Specification of KET format for macromolecules:
KET_macromolecules_specification.pdf
In case of variant monomers/monomers groups/hydrogene connections or connections without the link to monomers it needs to show an error.

Implementation details

Algorithm is following:

1. Iterate over an root.nodes array.
   1.1. If node.type === 'monomer' then create a command for new Monomer creation. Fields origin.x, origin.y should be used for coordinates. Field templateId should be used to find the template in library and take the type of monomer and label.
   1.2. If node.type === 'group' then show error.
   2.1. If node.connectionType === 'single' and node.endPoint1.monomerId !== undefined then create new PolymerBond by using endPoint1.monomerId and endPoint2.monomerId fields as a reference to monomers and endPoint1.attachmentPointId and endPoint2.attachmentPointId as attachment points. if there is no attachmentPointId field for some endPoint then do not set a specific attachment point to Monomer, just create a bond. Show error if node.endPoint1.monomerId === undefined or node.endPoint2.monomerId === undefined or node.connectionType !== 'single'