ImgOpener: remove rawtype ImgPlus

Converted all raw ImgPlus uses to ImgPlus<?>. This is to allow consuming
code to not have to worry about rawtypes warnings.
fix: imgopener
ImgSaver: remove type param from ImgPlus

Refactored all the typed ImgPlus signatures from <T extends RealType &
NativeType> to wildcards.

The type of the ImgPlus doesn't really matter for the writing algorithm,
and given that ImgOpener can't always guarantee the returned ImgPlus
type, requiring a generic parameter restricts the potential for
pipelining between ImgOpener and ImgSaver.

Had to refactor the ImgUtilityService#makeType(RealType) method to
accept an Object instead. This parameter is being type checked anyway in
the actual implementation, and given that Img's are generic typed on
<T>, and thus Objects and not just RealTypes, it makes sense to take
Objects and not RealTypes.
IO: remove rawtype ImgPlus

Refactored all methods with a generic parameter to use wildcards
instead, now that both ImgSaver and ImgOpener do not necessitate
rawtypes/type parameters.
IO: actually catch exceptions

The javadoc for the IO utility class indicates that all exceptions
should be caught automatically, with nulls returned if there is a
problem, but many signatures did still throw exceptions.

The javadoc intention was the intended function of the IO class, thus
it has been updated to catch and log errors.