231 save observation not working

[AllanEngland]

Finish the GUI functionality to support multiple targets per observation. Should also fix any errors that were happening when adding and editing observations.

[DJWalker42]

~Just to point out that this is effected by the empty strings being fetched as null/undefined when the 'notes' field of a timing window is left empty. You can see this when you create a new proposal, add targets, add a technical goal, create an observation with a Timing Window but leave the notes blank, then click on the 'Edit' button for that observation. But this is a separate issue.~

Obviously, this issue is relevant to master - not just this branch, so I've made a specific, separate issue, this branch should be merged.