Add support for tiered drop rates and tools

[timbru31]

Originally reported from kamziksvk via the Spigot forums:

Is there any way how can I increase the chance of dropping spawner via permissions? For example:
Player: 40%
Vip: 50%
Vip+: 60

[timbru31]

Follow up comment:

Mybe you can implement also possibility for different tools... for example: stone pickaxe 5%, iron 10% etc.

[timbru31]

Follow up comment:

Is it possible to add permissions for this for certain groups/players?

For example

silkspawners.dropchance.50
silkspawners.dropchance.70
silkspawners.dropchance.80

[smscentras]

From 2017 year feature request and there is no 1000% necessary feature? omg, dead plugin.