a form field has these values:
  valueDefault
  valueReceived
  valueInternal
  valueDisplay

read the class documentation about those.

when the form gets submitted valueReceived gets set to exactly what we got.
this will never be changed.
inputManipulate() works on this value, for example it may trim what we got. 
hrm, let's make an example:
the form field has the bsDataType 'date' and the bsDataInfo 4. so we expect 
to get an eu-style date like '15-01-2003'. 
now the user submits '15.1.03 '. 
the value gets trimmed, and then converted to what we want.
valueInternal will be '2003-01-15' while valueDisplay will be '15.01.2003'.

this gets done in inputManipulate(). later inputValidate will validate the 
valueInternal().



