BATCH-2041: Add support for reading excel files

This commit adds support for reading Excel files. Both JExcel and Apache POI are supported. Support for reading Excel files has been designed similar to the support for reading flat files.

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Small naming configuration thing.  Most of the classes that implement this bean property creation, we've called `BeanWrapper*`.  So in this case, it would be `BeanWrappreRowMapper` (see `BeanWrapperFieldSetMapper` and `BeanWrapperFieldSetExtractor` as examples).