Update documentation/manual/Migration.md
Update documentation/manual/Migration.md

Add note on move of form() methods to Form.
Shenker93/playframework,wegtam/playframework,Shruti9520/playframework,hagl/playframework,richdougherty/playframework,rajeshpg/playframework,zaneli/playframework,aradchykov/playframework,mkurz/playframework,hagl/playframework,marcospereira/playframework,richdougherty/playframework,hagl/playframework,rajeshpg/playframework,ktoso/playframework,aradchykov/playframework,richdougherty/playframework,wsargent/playframework,ktoso/playframework,rajeshpg/playframework,ktoso/playframework,mkurz/playframework,Shruti9520/playframework,playframework/playframework,zaneli/playframework,wsargent/playframework,hagl/playframework,rajeshpg/playframework,ktoso/playframework,marcospereira/playframework,Shruti9520/playframework,Shenker93/playframework,wegtam/playframework,playframework/playframework,zaneli/playframework,zaneli/playframework,mkurz/playframework,wegtam/playframework,Shruti9520/playframework,marcospereira/playframework,benmccann/playframework,benmccann/playframework,richdougherty/playframework,Shenker93/playframework,wsargent/playframework,aradchykov/playframework,mkurz/playframework,Shenker93/playframework,wsargent/playframework,aradchykov/playframework,playframework/playframework,wegtam/playframework,marcospereira/playframework,benmccann/playframework,benmccann/playframework