ND2: ignore invalid image offsets

Fixes QA 7534, #11305.
ND2: rework text annotation parsing so that dimensions are not overlooked

Fixes #12205.
ND2: set SizeT to the number of offsets if there is no dimension metadata

See #10773.
Do not adjust offset count if only one offset is present
One more fix to prevent equal-size planes from being ignored
Fix channel metadata population for multi-series data
Merge pull request #1199 from melissalinkert/rebased/develop/nd2-part-3

Nikon .nd2 fixes, part 3 (rebased onto develop)