Address various Matlab documentation issues raised by Simon

- Fix various typos in the documentation page
- Set default thumbnail width/height to 48 pixels
- Do not expose getImages(s, 'project'/'dataset', []) - not working in 4.4.7
- getObjectsXXXAnnotations(s, ids) does not support loaded objects yet
Fix capitalization of object names (use image rather than Image)
Merge pull request #348 from sbesson/matlab_fix

Address various Matlab documentation issues raised by Simon