Customizing the Dialog

I would like to customize the ACTA Dialog in that way how your library is currently written it is required to edit your source files, which makes it less portable.

I implemented a Factory (`DialogBuilderFactory`) to inject a custom dialog builder and an option to define a layout which should been used for asking the user for feedback directly in the ACRA annotation with `resDialogLayout`.

I made it also possible to put buttons into the custom layout, it has to use the id `android.R.id.button1` for the positive (send) button and `android.R.id.button2` for a negative (cancel) button.

PS: Sorry for the useless merge commit I thought you where using git flow so I made my initial changes on the dev branch.