In Json InspectorHandle use .toString() to get string value

Method .getTextValue() that was previously used returns null for
all that is not a string. However, it make sence to perform
conversion to string from json map or array, when string type was
requested.

For example:
    SELECT val FROM tbl
    LATERAL VIEW explode(json_split('[{"a": 4, "b": "f"}]')) x AS val;

will output:
    {"a": 4, "b": "f"}

as expected. However, without that patch, output will be "NULL".
Merge pull request #80 from wonder-mice/mainline

In Json InspectorHandle use .toString() to get string value