Move SPI changes to end of 0.75 release notes
Update 0.75 release notes
Update overview documentation
Exclude concepts documentation

This needs more review before it can be published
Allow ':' in JsonPath path segments but not subscripts
Extract assertInvalidPath test helper
Fix warnings in JsonExtract
Do not allow whitespace in JSON path expressions
Remove approx_avg from documentation
Update 0.75 release notes
[maven-release-plugin] prepare release 0.75
[maven-release-plugin] prepare for next development iteration
Add support for distributed index joins

This is enabled via a config option and is default off.