If an extension is loaded at project-load time, there won't be any
targets. In that case, `handleExtensionAdded` now skips target-specific
steps.

This change also adds a filter for JSON block info to support upcoming
block separators, which have XML but no JSON.

- Call scrollToCategoryByName('My Blocks') after custom block is created
- Cannot assume custom blocks section will be last category
- May pose issue during localization efforts

Showing/hiding 'more options' in the different types of variable prompts based on var type provided from scratch blocks

Localizes the pen extension:
- loads all pen locale information - may want to consider dynamically loading locales later.

The VM refreshWorkspace will eventually lead back to onWorkspaceUpdate,
which will call refreshSelection itself.

This reverts commit 5b9e8aa0, reversing
changes made to 4cb65dc5.

To prevent loading scratch-blocks default toolbox

Also, delete `static-blocks.xml` which shouldn't have been added in the
first place.

This shouldn't be required.