Thrift: Fix xsd:sequence and xsd:all minOccurs/maxOccurs generation

Thrift: Fix xsd:sequence and xsd:all minOccurs/maxOccurs generation

The minOccurs and maxOccurs attributes should appear on the elements, rather than the containers.

for a thrift struct, we produce:
<sequence>
<element name="some_element"> <!-- max is implicitly 1 -->
<element name="some_optional_element" minOccurs="0"> <!-- max is
implicitly 1 -->
...

for a thrift list, we produce
<sequence>
<element name="the_list_element" minOccurs="0" maxOccurs="unbounded">
</sequence>

for a thrift struct tagged with xsd_all, we produce

<all>
<element name="some_element" minOccurs="0"/>  <!-- max is implicitly 1
-->
</all>

Reviewed By: mcslee

Test Plan: sandbox

Revert Plan: revertible

Notes:

git-svn-id: https://svn.apache.org/repos/asf/incubator/thrift/trunk@664962 13f79535-47bb-0310-9956-ffa450edef68