Add loadFromChemicalJson RPC method

This adds a new RPC method named loadFromChemicalJson which will
load and display a molecule from its Chemical JSON.

Change-Id: I1c0f617e3d8f44d246a6fef11c91ddbdfa8ae8d4
Merge topic 'load-molecule-from-json' into master

2604a9bf Add loadFromChemicalJson RPC method