Fix indentation for HTML with line breaks

Previous indent:

  a<b>c
  d

  ==>

  NaN<b>Nc
  Nd

New indent:

  a<b>c
  d

  ==>

  Na<b>c
  Nd

("N" = "&nbsp;" * 4.)
HTML indentation: return quickly for ''
Change "strength" fields to float
Fix displaying hidden notes
Version set to 0.14.2