Spigot-CraftBukkit 1.8 compatibility. Implements #442

This branch holds the visible progress on a 1.8-compatible EchoPet release. Anything here should **only** be used for testing purposes (which will be conducted once this branch is closer to completion. This pull request also implements issue #442.

The following list will be updated as progress is made.

Currently completed:
- [x] General module update, as per usual (NMS updates, mostly for the obfuscation changes from v1_7_R4 -> v1_8_R1).
- [x] Updating of dependencies ([PowerMessage has been updated to support the few changes in protocol handling](https://github.com/DSH105/PowerMessage/commit/3c18d185d06cfd0e717e055c06a50f699f5f4861)).
- [x] Entity datawatchers are still mapped to the 1.7 values; this needs to be updated to support 1.8 clients (causes client crashes).

Once I am satisfied with the stability of the 1.8 module, it will be merged into the master branch and published to BukkitDev.

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Known issues (thanks @mibby for helping out in IRC with these ;D):
- [x] Blaze pet data menu does not contain 'fire' option.
    - Fixed in https://github.com/DSH105/EchoPet/commit/0c56da7ea69a7f78bef6b510b35383b52c540902.
- [x] Baby horses disconnect clients.
    - Fixed in https://github.com/DSH105/EchoPet/commit/24a36e157ce08e9e16ca4ea5669b4780035a4cbf.
- [x] Pet selector does not work when certain pets are on top of your head.
    - Fixed in https://github.com/DSH105/EchoPet/commit/8675bf61e37ae0a3e96cdfbbbc436ba75ca015cf.
- [x] Right-clicking pets no longer opens up the pet menu.
    - Fixed in https://github.com/DSH105/EchoPet/commit/bb26c04e31db916c7294d1724349b6e6e9c85d57.
- [x] Human pets crash the server: http://paste.ubuntu.com/9472027/.
    - Fixed in https://github.com/DSH105/EchoPet/commit/67444aaf7359b1677c052d2c0e2ba9534f4f2196.
    - As per https://github.com/DSH105/EchoPet/commit/410f879c83ba939a87566aacc83721f251aeba7b, human pets no longer crash the server. They do, however, appear as zombies (which I don't currently have a fix for yet).
    - https://github.com/DSH105/EchoPet/commit/3e459d93e1eace85351bc51436303ae471a23ea1.
    - Human pets are now disabled for 1.8: https://github.com/DSH105/EchoPet/commit/4aa3fac05e0c04a9a2497ea492ab76b0ef23b1bd.
- [x] PigZombie pet - Unable to toggle villager option in pet menu. Closing and reopening the GUI shows it is toggled on/off, but the pet does not change at all. No errors.
    - Option removed from PigZombie pets ('villager' PigZombies are no longer allowed), as per https://github.com/DSH105/EchoPet/commit/80a023423e4c8833eca24784390c800ba6b6831d.
- [x] Baby wolves disconnect clients (same as baby horses).
    - Fixed in https://github.com/DSH105/EchoPet/commit/42392f8c5f226c4a477565726bc15605cdd4c479.
- [x] Toggling 'angry' wolf status when the 'tamed' status is already active only affects the tail (should change the face as well).
    - Fixed in https://github.com/DSH105/EchoPet/commit/315ad278f0869e67bf81c1eecdf83392de269503.
- [x] Some status changes are not reflected appropriately in the GUI menu (~~e.g. hat, baby, blaze 'fire', pig/horse saddling, 'chested' horses, wither 'shield', 'sheared' sheep~~ - essentially everything except the pet riding option).
    - Fixed in https://github.com/DSH105/EchoPet/commit/b752fbaedd07a8d14711b5e4c9338e94be1ecdaf.
- [x] Ride speed is unusually fast (perhaps drop the default of 0.25 down to 0.2).
    - Fixed in https://github.com/DSH105/EchoPet/commit/d9031e6dd7f0b2daf77ea21f91a4f2a32df42433.
- [x] Particles are temporarily disabled until compatible with 1.8.

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Known issues (but are not being fixed, mainly likely because they can't be):
- Pet name tags are only visible on hover (1.8 client issue I presume).
- When set as a hat, most of the pets obstruct the player's view (e.g. silverfish, squid). Likely a client side 
change.
- Saddles and chests aren't visible on baby horse pets.
    - Identical behaviour occurs with normal horse entities.
- All pets put on your head are constantly looking down, as if it is in a constant state of tracking the player.
    - Identical behaviour was observed by placing a rider on top of a pet - **correct me if you achieve different results**.
    - Fixed in https://github.com/DSH105/EchoPet/commit/82f03277b65eabc2b86fff4b0b206a873e1fed98 and https://github.com/DSH105/EchoPet/commit/2884286798ddfd10e705b0768c35e6376875a65f (**not confirmed**).
- Right clicking a horse pet resets your screen rotation to that of the horse.

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For those wishing to test, [builds are temporarily enabled over on my CI](http://ci.dsh105.com/job/EchoPet-v2%20for%20v1_8_R1/). **Important: These builds should NOT be used in production and are experimental *snapshot* builds. You should really only be making use of them if you're helping out in the testing phase.**