Additional nulling support.

<parameter name='si.' value='' /> today this would not clear out array values such as si[0], si[1], si[2], etc. This change will make it so this clears out array values as well as non-array values.

The code also supports removal of a single element via                 <parameter name='si[0].' value='' /> this would delete values starting with si[0] but would not affect other array values like si[1], si[2], etc.