Significant UI changes in the develop branch

[ahyatt]

Hi everyone,

I'm pushing some significant changes to the develop branch. I'm getting rid of something that has been a longtime issue, namely the metadata section on note capture/editing. Now, instead of that, you can change properties via commands, and they are shown on the header-line. This should make the notes buffer much better behaved in general.

There's more changes, and I have some plans for some useful new functionality as well before this goes to a new version. I anticipate it taking another few weeks before that happens.

Any feedback would be appreciated on this change!