only show messages export section if we have reords #421
Removed deprecated forms export code and paths. #421

Warning: the following URLs are no longer supported:

```
/{form}/data_records.csv
/{form}/data_records.xml
/form_data_records.xml
/form_data_records.csv
```

Use `/export/forms/{form}` path instead with following query params.

startkey/endkey

    The startkey and endkey arrays represents the following fields on
    the record:

        [valid, form code, reported date]

        or

        [valid, district uuid, form code, reported date]

    Appending a `{}` value at the end of the array represets a wildcard
    and is always required in the startkey because ordering is set to
    descending in the rewrite.  To retrieve all records use `0` as your
    endkey reported date value.

    Examples (ignore newlines):

    Valid CSAC form submissions:

        /export/forms/CSAC?
            startkey=[true,"CSAC",{}]&
            endkey=[true,"CSAC",0]

    Valid CSAC form submissions after Date(1385852400000):

        /export/forms/CSAC?
            startkey=[true,"CSAC",{}]&
            endkey=[true,"CSAC",1385852400000]

    Valid CSAC form submissions from District
    d049925d-72da-063b-24ff6532734a81b0 after Date(1385852400000):

        /export/forms/CSAC?
            startkey=[true,"f0ca29da38d49ccd0b04cd6bb30be864","CSAC",{}]&
            endkey=[true,"f0ca29da38d49ccd0b04cd6bb30be864","CSAC",1385852400000]

tz (default: 0/GMT)

    Given a timezone offset in minutes, formats date values appropriately.
    Default is GMT.

    Examples:

        -60 formats timestamp fields for GMT +0100.
        120 formats timestamp fields for GMT -0200.

format (default: csv, options: xml,csv)

    Allows specifiying file output type. xml value is SpreadsheetML.
updated tests for new export_data_records list function. #421

lists.data_records_csv and lists.data_records_xml have been replaced
with lists.export_data_records.

startkey and endkey are also required query parameters.