[#12] Add source to semantic search
This PR modifies the semantic search workflow to also pass the source
property to the API.
It affects the document results, the staged documents, and the ones in My Library.
The documents saved to My Library now also store their source
property - to be used in the future when requesting the chunk information.
An error message is now displayed when trying to find the similar documents for a document previously added to the Library, which doesn't contain the source
property.
And finally, the menu options in My Library have been rearranged.