Allows admins to configure Lexorank rebalancing triggers

Problem Definition

Currently, Jira will schedule Lexorank rebalancing in 12 hours since the longest rank on the instance reaches 50 characters and will perform an immediate rebalance once the longest rank reaches 100 characters.
Those values might not be ideal, the threshold of 50 characters (out of the 250+ allowed) could be low in many cases.

Suggested Solution

Giving administrators an ability to configure those values would help with reducing issues caused by often lexorank rebalancing.