rename init_shrink and move it to initialization

docs/source_docs/user_guide/inputs/initialization.rst

@@ -12,6 +12,9 @@ The following inputs must be preceded by ``mfix`` and determine how we initializ
 +----------------------+-----------------------------------------------------------------------+-------------+--------------+
 | initial_iterations   | Number of pressure iterations to execute before time-marching         |  Int        |    3         |
 +----------------------+-----------------------------------------------------------------------+-------------+--------------+
+| scale_init_dt        | Factor by which ``dt`` is scaled in the initial iterations and step.  |    Real     |  1.0         |
+|                      | Must be a value <= 1.0                                                |             |              |
++----------------------+-----------------------------------------------------------------------+-------------+--------------+
 
 
 +----------------------+-----------------------------------------------------------------------+-------------+--------------+