Removed code duplication, made code more readable

I think PasswordModifyExtendedOperation.processExtendedOperation() should call setMatchedDN() ?



AbstractOperation.java:
Extracted methods processOperationResult() and setResults().

PluginResult.java:
Extracted PluginResult.OperationResult interface out of several types.
Removed duplicate javadocs.
Used {@code} in javadocs.
Fixed typos.

SynchronizationProviderResult.java:
Now extends PluginResult.OperationResult + removed duplicate declarations.



*OperationBasis.java:
Called processOperationResult() and setResults().
Used static imports for DirectoryServer.*.
Removed useless comments.

LocalBackend*Operation.java
Called processOperationResult() and setResults().
Used static imports for DirectoryServer.*.
Removed useless comments.
Extracted method getAccessControlHandler().