Switch from serialize() to print_r(), replace true/false/null values with their text representation

serialize() is still not a perfect solution when sending objects ("__PHP_Incomplete_Class")


Signed-off-by: Peter Legierski <peter@legierski.net>

Signed-off-by: Peter Legierski <peter@legierski.net>
Bump version to 1.5.1

Signed-off-by: Peter Legierski <peter@legierski.net>
Merge branch 'feature-data' into develop