New XML Wizard fixes

New XML Wizard fixes

1. Make the LinearLayout default width and height values be
match_parent for Android 2.x and up, fill_parent for older.  This
fixes issue 13481: ADT creates layout resources with fill_parent
instead of match_parent

2. Give the Name field initial focus rather than the Project field,
since you usually don't want to edit the Project field and more than
once I've accidentally edited the project name instead.

3. Don't require the user to manually type ".xml" as a suffix since
it's required anyway. If you type "foo", it will create "foo.xml". You
can however type "foo.xml" (and you cannot type any other extensions.)

Change-Id: Ibd03bb73e283b02991662de6ab889f647554b7d6