[B+C] Add ability to make items glow. Adds BUKKIT-4767

### The Issue:
There's no way to make an ItemStack glow without adding an Enchantment to it. Some plugins are using reflection and/or NMS access to do it.

### Justification for this PR:
This adds a simple way to make an ItemStack glow.

### PR Breakdown:
##### Bukkit
Added hasGlow() and setGlow(boolean) methods to ItemMeta.
##### CraftBukkit
Implemented hasGlow() and setGlow(boolean) methods in CraftMetaItem and make related changes to the class. We make use of the difference between a null Enchantments map and an empty Enchantments map. The glow effect without enchantments is achived by having the 'ench' NBT tag without any enchantment.

### Testing Results and Materials:
Test Plugin: https://github.com/Ribesg/TestPlugin/tree/BUKKIT-4767
Build everything yourself to test it as we're not allowed to link CB builds here.

### Relevant PR(s):
CB-1363 - https://github.com/Bukkit/CraftBukkit/pull/1363 - Associated CraftBukkit PR

### JIRA Ticket: 
BUKKIT-4767 - https://bukkit.atlassian.net/browse/BUKKIT-4767