Add dropdowns for 'parent' and 'child' fields of 'joint' (issue 48 fix)

[pbeeson]

This fixes Issue #48, but builds upon PR #59.

[gavanderhoorn]

I'll check #70 tomorrow. If that works, could I ask you to rebase so this PR only includes f916110 then?

fyi: for proper attribution, you might want to correct the email address for the committer. Right now it just shows 'Stephen Hart', but github can't link that to the account name.

[pbeeson]

If #70 goes through, I would think this PR would update t only show f916110. If not, we can rebase it. Perhaps it might be best for @swhart115 just to do that and submit a new PR of his own so that it recognizes his credentials.

[gavanderhoorn]

I've just tested f916110 cherry-picked on top of a merge of #73 and #70, but I couldn't create a valid tree from scratch.

Could I ask you to retest this on top of #73 and then see what happens if you merge in #70?

[pbeeson]

@swhart115 Can you handle this test?

[gavanderhoorn]

I realise "it doesn't work" wasn't really helpful.

What I observed was that although I could change the parent of a joint, that change didn't seem to be picked-up by the rest of the application (ie: propagated beyond the property itself). Could be that a emit valueChange(..) or similar is missing?

[gavanderhoorn]

@swhart115: I broke this PR (as in: it can't be merged easily), but that is my problem, not yours.

If you follow @pbeeson's suggestion however (just take f916110, rebase it and submit a new PR or forcibly update feature/issue-48-fix), it would be easier.

[pbeeson]

Replaced by PR #78