inline_entity_form 8.x-1.0-alpha3

Changes since 8.x-1.0-alpha2:

• #2611956 by axe312, Denchev, mikgreen, slashrsm: If inline entity is newer (changed more recentry) then node - validation fails
• #2612790 by anil280988, jeroen_drenth, rashid_786, sanja_m: Convert t() function calls to $this->t() in field widget implementations
• #1706882: #entity_builders are not invoked
• #2618154 by joshi.rohit100: Move/rename the inline entity handlers
• #2490914 by Denchev: Use autocomplete element for autocomplete feature
• Clean up InlineEntityFormSimple.
• Remove the argument from InlineEntityFormBase::getInlineEntityForm().
• #2618148 by vasike: Rename the "inline entity form" handler key (annotation)
• #2609020 by slashrsm: Unable to reedit entity when two IEF fields are present
• #2597710 by slashrsm: Fatals in validation of inline form
• #2612070 by bojanz: Rework EntityInlineEntityFormHandler::tableFields()
• #2512678 by dbolinovski, slashrsm: Write tests for IEF multiple field widget
• #2597602 by slashrsm: Serialization errors in RC1