Introduced manual non-annotation based init methods.

Added the additional init methods as discussed.  I felt a configuration builder helped here as instantiating the ACRAConfiguration was a bit messy.  Here's the resulting manual setup:

```
ACRA.init(application, ACRAConfigurationBuilder.builder().setFormUri("uri"));
```

or if you static import ACRAConfigurationBuilder:

```
ACRA.init(application, builder().setFormUri("uri"));
```

I also avoided adding the formKey as it is mentioned as depreciated.  BTW, could you in the `ReportsCrashes` set the `String formKey() default "";`, `@Depreciate` it, then remove it in a later release?