[FEATURE] Fallback/default case for SwitchViewhelper

In order to provide the full functionality known from the
switch/case PHP function, a default case possibility is
introduced. Use it like:
<f:switch expression="{person.gender}">
  <f:case value="female">Mrs.</f:case>
  <f:case value="male">Mr.</f:case>
  <f:case default="TRUE">Mrs. or Mr.</f:case>
</f:switch>

Resolves: #49371
Documentation: #54283
Change-Id: I6b71ec39173ab957aa392bd595a65ceddadc81c9
Releases: 6.2
Reviewed-on: https://review.typo3.org/23739
Reviewed-by: Cedric Ziel
Tested-by: Cedric Ziel
Reviewed-by: Anja Leichsenring
Tested-by: Anja Leichsenring