[Scenario] Add combo box to tag control
[Scenario] Add component renderer to tag combo box
[Scenario] Set tag combo box text

Force tag combo box in Activity
component's info view to always
read "Add a Tag" even though
it is not among the selectable
items by exposing it as though
it were an editor for custom
text.
[Scenario] Add tags when combo box selection made
[Scenario] Add spacing in tag control combo box
[Scenario] Fix logic error in Activity tagging

Activity exposes tags by polling
children and aggregating their tags.
The list returned is lazily instantiated
but the incorrect co-location of
the addition of tags to the list in
that block was causing all but the
first tags on an Activity to be
ignored.
[Scenario] Fire change when tag added via UI
[Scenario] Preserve component order when tagging
[Scenario] Create container for tag removal
[Scenario] Render tag container as capsule
[Scenario] Match background color in tag container

Use the background color from the
combo box in the tag container, to
ensure that the two match.
[Scenario] Draw tag capsules smoothly
[Scenario] Add X icon to tag capsules in Info UI
[Scenario] Change X icon in tag UI to button
[Scenario] Remove highlights from tag removal button
[Scenario] Hook up tag removal button

When tag removal button is clicked
in the activity tagging UI, remove
the tag and fire change listeners
so that Info View can complete the
object save and UI update.
[Scenario] Make tag removal capsule narrower
[Scenario] Left align tag removal capsules
[Scenario] Prevent removal of last tag

If a tag component in the tagging UI
is the last manifestation of a
component, we don't want to let the
user remove it - this would be an
unintentional delete.
[Scenario] Mark tags property as mutable