FIX Resolve issue with multiple dependent rules

Implementation of the rules required that a dependent field could only rely on one implementation. This patch joins all those dependencies together in one function to exclude. Tests / a rewrite of this behavior is on the horizon.
NEW Migrate submissions section to a GridField instance. (Fixes #94)
NEW Filter submissions by created date
FIX use sqlquery for building sort query
Master requires SS3.1
Fix composer syntax
Update nl_NL.yml

Dutch language improvements
Update UserDefinedForm.php

Changed two typos: UserDefinedform must be UserDefinedForm
Merge pull request #97 from mschilder/patch-1

Update nl_NL.yml
Merge pull request #98 from mschilder/patch-2

Update UserDefinedForm.php
Don't use submodules until github downloads support
FIX: fix submissions grid field in 3.0 versions (#96, #100)
Removed cached submodule leftovers
Added files from old submodules directly
Merge pull request #101 from markguinn/master

Added submodule files back into vcs
FIX: update templates for 3.1 template syntax
FIX: update DropdownField usage for 3.1
FIX: if type has not been selected, do not attempt to create a new field
Merge branch 'master' of https://github.com/silverstripe/silverstripe-userforms