Command Center: Add a button to invoke the cmd+k interface in site view

[jameskoster]

The Command Center is a powerful tool, but there's no obvious way to summon it in Site View.

An icon button in the 'site hub' area seems like a reasonable placement. To begin with a search icon might work, but this doesn't really capture the full scope of this feature, so we might consider other options.

[richtabor]

I think we should roll with the search icon. It's common enough and relative to the searching-for-commands action.

[jasmussen]

Agreed, let's go with the search icon for 6.3 and near future, then we can explore if/when it evolves into something else!