Implement a GetSize() function for the ImageMetadata class

Description

With OTB 7.4, I use keywordlist.GetSize(). It is not possible with OTB 8.0 and ImageMetadata since it doens't have such a function.

added refactoring label

assigned to @julienosman

@julienosman it is GetSize() ;)

We use this in CARS so we cannot do the upgrade to 8.0.0.

Maybe also discuss on how to check that the structure is empty or not (maybe not only check size for that in the structure API).

Thanks for getting that in next OTB release

changed the description

mentioned in merge request !872 (merged)

mentioned in commit 7c6de401

closed with merge request !872 (merged)

changed milestone to %8.0.0