Add good defaults to XML Schema Import Wizard

We should choose good defaults throughout this wizard, such as:

• Pre-select the "from file system" option (vs. "via URL") on the first page
• Auto-populate the "From directory" field to the user folder and remember whatever the user finally chooses thereafter. Working with a selection dialog that only allows you to choose a folder is too different from the norm to not be awkward. Always takes me a few seconds to remember why the file I'm trying to select is grayed-out.
• Auto-populate the "Into folder" field if there is only one folder, a single project folder, in the workspace.
• Provide a way to create a project so the user doesn't have to exit the entire wizard if they forget to first do that.