moved flexbox mixins to core, upgraded enketo-core with first version of likert widget
updated enketo-core and xsl sheet modules for Likert widget
fix style of mark-as-draft button
Likert fixes
sidebar slides on top of form now, closes #251, closes #249, closes #248
final fixes for likert in submodules
Merge branch 'likert' of https://github.com/MartijnR/enketo into sidebar