use flt_rst instead of flt
engine fix instance value building
fix fliter text indent for ActionFinish
common.xpt.vim: Echo returns action dict
engine: xptemplate.vim by default text is to be built
engine: remove 'toBuild', use flt_rst.action == 'build'
engine: default value accept action 'text'

fix Echo() for default value
engine: HandleDefaultValueAction refined
engine: s:FillinLeadingPlaceHolderAndSelect simplify