Fix headless dialog with boolean parameters

Daniel Hornung recognized an issue where the headless dialog would not
work properly. The culprit was that the same label was used for multiple
purposes in the macro options: the file name and the "open all" flag.

In this particular case, it should be non-fatal, though, because the first
use requires a file name while the second, being a flag, requires *no*
value. Example: "open=/tmp/blub.raw" should not match the "open all" flag,
while "open=/tmp/ open" should (yes, it is confusing).

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Add a test for headless boolean parameters

To make sure this never breaks again.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Adjust to 1.48s' GenericDialog

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Rewrite findBooleanMacroParameter() completely

The new version reads much easier, at least in this developer's
opinion.

Daniel Hornung pointed out a problem with the previous code. This
change fixes it, and other edge cases, too.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Test more boolean parameter cases

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>