show reason if readable forms does not work

in addition to downgrading to old submissions
fix "next" url in latest user api

http://manage.dimagi.com/default.asp?110111
Merge pull request #3277 from dimagi/debug-readable-forms

show reason if readable forms does not work
pull out a get_bind method on XForm class
add group and type information to get_questions
fix get_questions to treat repeat groups correctly as a unit

previously had an entry for the group (with a label)
followed by an entry for the repeat node (without a label)
Merge pull request #3271 from dimagi/user-api-fix

fix "next" url in latest user api
add support for displaying question hierarchy
make readable form data hierarchical by group/repeat
make _index_on_fields a tad more explicit
Merge branch 'vellum-includes' into autostaging
Merge branch 'multimedia-case-properties' into autostaging
Merge remote-tracking branch 'origin/sql-dailyformstats' into autostaging
Merge branch 'use-build-id' into autostaging
Merge branch 'pretty-user-display' into autostaging
Merge remote-tracking branch 'origin/report-issue-upload' into autostaging
Merge remote-tracking branch 'origin/autoselect' into autostaging
Merge branch 'better-get_questions' into autostaging
update submodule refs