Added creature spawner methods

**The Issue**
In 1.5 or so mojang added some new abilities for monster spawners. I
added some methods to use that. Not everything is implemented, only
simple changes

**Justification for this PR:**
The code for these methods is already in CraftBukkit, it just isn't implemented in the API. For a plugin I am working on, this would be usefull. There are also other plugins that give the ability to change spawners, but those aren't using the Bukkit API

**PR Breakdown:**
Bukkit: Adds methods to get and set the minimum and maximum delay of a spawner, the required range a player should be in, amount of entities to spawn in one go, the maximum nearby entities, and the range of the spawner.
CraftBukkit: Implements said methods.

**Testing Results and Materials:**
All methods where tested using a plugin I'm currently developing.
Precompiled: Craftbukkit: http://sdrv.ms/117j9P8

**Relevant PRs:**
Bukkit: 

**JIRA Ticket:**
JIRA is under maintenance right now