Move redisearch index to persistent store

[ankush]

• move it to redis_queue
• Add redisearch module in press on redis_queue instance too (right now it's added only on redis_cache)

This is proper fix for https://github.com/frappe/gameplan/commit/b6eddbd9a238d4f9d7e2af8b6bbb6a9c1ed7895b where index gets dropped constantly from frappe.clear_cache()

[blaggacao]

Please also declare the dependency on redisearch.so on the way, e.g. in the readme.