Merge migration moved into gh-book into bookish-split.
Redo of migration view move into gh-book.

See b913940cd6d05017d03b8255915726c6c3777b78 and
715eb7b0687df000d2a36088b3a1eb9a34bbb507.
Added ctags updating script, for development purposes.
Manually merge with ghbook#master