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.
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.
Merge branch 'remove-imgsaver-generics'

Provides fixes to the ImgOpener, ImgSaver and IO utility class. The fundamental
goal here is to allow ImgPluses returned by ImgOpener to be immediately used by
ImgSaver, without rawtype warnings.

Closes #97