This allows to use %n|% to add a number if needed for unicity.
Args are mandatory, start, step.
Default values for these are 0, 1, 1.

issue #5882

The code tries to support generators from modifiers so that random
 string and future number modifiers can return a generator and not store
 large arrays in memory.

issue #5882

It’s a bit less readable but we have to call array_values to avoid a
 fatal error.

issue #5827

For PHP<7.0, we fall back on openssl_random_pseudo_bytes from openssl module.

issue #5843

Instead of less readable func_get_args and call_user_func_array

issue #5827

Useful for filling shadowExpire with templates, this works by giving
 'epoch' as format in the date modifier.
Result is the number of date since epoch, as is needed in shadowExpire
 field
(Standard format U is number of seconds since epoch, aka timestamp)

issue #5746

issue #5745

There are some left in datepicker.js because of a bug in the sniffer,
 I did not find a way to fix that yet.

issue #5690

Fixes #5358 Fixed ImageAttribute usage in templates. Added special %% string start for template values

Remove the useless trailing whitespaces at the end of this line
Add one whitespace between the colon and the value.

Signed-off-by: Mortier Benoit <benoit.mortier@opensides.be>