Improve spatial package.html to compare Strategys [LUCENE-4223]

Spin off from #5245. One of the most important parts of using the spatial module is deciding which Strategy fits your needs. We should improve the package.html documentation so that it compares the Strategys, focusing on:

- Underlying index format (lon/lat numeric fields vs grid terms vs ...)
- Multi-value support
- Indexable Shapes
- Queryable Shapes
- Query operations

---
Migrated from [LUCENE-4223](https://issues.apache.org/jira/browse/LUCENE-4223) by Chris Male, updated Jul 23 2012

Start with the spatial module's package.html and inspect the available Strategies and their existing documentation. Update the comparison to cover underlying index format, multi-value support, indexable and queryable shapes, and query operations; done means users can compare the Strategies against all listed criteria.

Written by the indexing model from the issue text.