Allow variables within strings in BooleanParser

[simonschaufi]

The following test case currently is not possible as the boolean parser either accepts strings OR variables but not both.

['\'{foo}\' == \'{bar}\'', true, ['foo' => 'a', 'bar' => 'a']],

I would expect this to be true. A workaround is to assign the string to a variable before with the f:variable-ViewHelper and then use the new created variable for comparison.

[s2b]

To clarify, this would be a use case for this (string concatenation within condition):

['{foo} == \'{bar} {baz}\'', true, ['foo' => 'a b', 'bar' => 'a', 'baz' => 'b']],

And I can confirm that this currently does not work.