add option to change GENERATION_SUFFIX

see https://github.com/excilys/androidannotations/issues/1209

this allows to set the `generationSuffix` via options. at the moment the same valule is used for all generated stuff (classes, fields, methods) where it before was `_`. But for a first look i already opened the PR.
Same here. We should keep `scopedObjects_` since `scopeObjectsImpl` would be weird.