* Weights are calculated per index and incorporate index level, global and primary related parameters
* Balance operations are executed based on a win maximation strategy that tries to relocate shards
first that offer the biggest gain towards the weight functions optimum
* The WeightFunction allows settings to prefer index based balance over global balance and vice versa
* Balance operations can be throttled by raising a threshold resulting in less agressive balance operations
* WeightFunction shipps with defaults to achive evenly distributed indexes while maintaining a global balance
Closes#2555
When setting cluster.routing.allocation.disable_allocation, it causes new indices primary shards to not be allocated. By default, new indices created should allow to, at the very least, allocate primary shards so they become operations. A new setting, cluster.routing.allocation.disable_new_allocation, allows to also disable "new" allocations.
closes#2258.