Make DashboardHelper a bit more configurable
Convert dashboard alias using dots with dashes

Using dots in an identifier is common in config files.
By converting it as `-`, it enables using the dashboard
alias as jquery selector.
Do not assume that saveDashboard is called via jquery-ui sortables

Custom themes may provide its own dashboard ui handling callbacks.
So, just do our primary task, ie save the dashboard info and
simply return when the ui argument is missing.
Do not initialize Dashboards when including admin.js

For the same reason as previous commit, themes may want to use their
own custom initializers
Remove Dashboard.debounce() since we can use _.debounce()
Don't initialize Admin when including admin.js

- Themes should initialize Admin themselves

  It should then decide for themselves whether they need to reuse the
  default behavior by calling the default initializers themselves.

- Refactor slide toggle initializer out of Admin.extra()

  The box slide toggle initializer is very similar to the dashboard box
  handling code. It potentially causes event handling conflicts for custom
  admin themes. Thus, move it out from Admin.extra().
Blogfeed: Fix DomId conflict + add utm_source
Rename Dashboards::admin_index to Dashboards::admin_dashboard
Implement Dashboards::index()
Registered dashboard widgets can now be enabled/disabled
Include Dashboards in bundledBundle list

This allows Dashboards to be displayed when a pending migration exists
even when no plugin.json is present.
Dashboards: Enable dashboard move[up|down]
Merge branch '2.2-more-dashboard' into 2.2

* 2.2-more-dashboard:
  Dashboards: Enable dashboard move[up|down]
  Include Dashboards in bundledBundle list
  Registered dashboard widgets can now be enabled/disabled
  Implement Dashboards::index()
  Rename Dashboards::admin_index to Dashboards::admin_dashboard
  Blogfeed: Fix DomId conflict + add utm_source
  Don't initialize Admin when including admin.js
  Remove Dashboard.debounce() since we can use _.debounce()
  Do not initialize Dashboards when including admin.js
  Do not assume that saveDashboard is called via jquery-ui sortables
  Convert dashboard alias using dots with dashes
  Make DashboardHelper a bit more configurable

Closes #557