Time format: Add hook for custom format (D7/D8)

There are several requests for a 'custom' time format in the Office Hours Formatter.
Instead of adding each of those formats, I propose to use :
D7: function hook_field_display_alter(&$display, $context)
D8: function hook_entity_view_alter(&$build, $entity, $display)

D8 introduced EntityViewDisplay config entities

In most (all) requests , a pattern can be found, which can be used in a simple string replace function call (str_replace).

So, the plan would look like:
- in the module, add an example of above hooks in office_hours.api.php, and document this somewhere.
- per custom project, add above hook and implement a str_replace
- alternatively, add an extra setting in 'field display settings' with the replace definition, Which is called by a hook that is implemented in the module.

Some examples are now documented in ofice_hours.api.php file:

// Remove separating space between time and ampm.
$formatted_time = str_replace([' am',' pm'], ['am','pm'], $formatted_time);
// Replace 'a.m.' by 'am'.
$formatted_time = str_replace(['am','pm'], ['a.m.','p.m.'], $formatted_time);
// Replace '9:00 am' by '9am'. (Separate lines to not destroy '16:00'.)
$formatted_time = str_replace([':00 a'], [' a'], $formatted_time);
$formatted_time = str_replace([':00 p'], [' p'], $formatted_time);
// Convert 'Open all day'.
// Translation can be managed on /admin/config/regional/translate.
$formatted_time = str_replace(['12a.m.-12a.m.'], ['Around the clock'], $formatted_time);
$formatted_time = str_replace(['00:00-24:00'], ['Around the clock'], $formatted_time);
$formatted_time = str_replace(['Around the clock'], ['All day open'], $formatted_time);
// Translate. Translations can be managed on /admin/config/regional/translate.
$formatted_time = t($formatted_time);

This is now implemented in v*.1-1.7

Additional feature request: in the field widget add a text(list) element, where the user can add each of the above translations, without using code.