[FEATURE] Support literal strings in boolean arguments

This change adds support for string literals in boolean comparisons.
String literals have to be surrounded by single or double quotes and
may contain escaped single or double quotes.

This is possible now:
<f:if condition="{foo} == 'foo'">

This is a port of the feature from FLOW.Fluid 1.2 from issue #6757.

Change-Id: I1799ff8c4187d33f47a2251404e59f87ff9cba1b
Resolves: #45316
Releases: 6.1
Reviewed-on: https://review.typo3.org/18156
Reviewed-by: Wouter Wolters
Tested-by: Wouter Wolters
Reviewed-by: Markus Günther
Tested-by: Markus Günther
Reviewed-by: Christian Kuhn
Tested-by: Christian Kuhn