Add Python 3 and modern Solr (7+) compatibility

[Copilot]

The library was Python 2 only and lacked support for Point field types introduced in Solr 7, preventing use with recent Solr releases.

Changes

Python 3 Compatibility

• Added compatibility layer for Python 2/3 differences:
  • unicode/basestring → text_type/string_types (as tuples)
  • cStringIO → io.StringIO
  • urllib/urlparse → urllib.parse
  • base64.encode() → base64.b64encode()
  • Exception syntax: except E, e: → except E as e:
  • Print statements → functions

Modern Solr Field Types

• Added support for Point field types (Solr 7+):
  • IntPointField, LongPointField, FloatPointField, DoublePointField, DatePointField
  • Int32PointField, Int64PointField (alternative naming)
• Maintained backward compatibility with deprecated Trie/Sortable field types

Example

# Schema with modern Point fields now works
schema_xml = '''
<schema name="example" version="1.6">
  <types>
    <fieldType name="int" class="solr.IntPointField"/>
    <fieldType name="long" class="solr.LongPointField"/>
  </types>
  <fields>
    <field name="id" type="string" required="true"/>
    <field name="count" type="int"/>
  </fields>
</schema>
'''
schema = SolrSchema(StringIO(schema_xml))  # Works in Python 3 with Solr 7+ schemas

Backward Compatibility

All existing APIs unchanged. Supports Python 2.7+ and Solr 1.3+.

Original prompt

create a PR to make this work for recent solr releases

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