Added ChatAPI

Suggestion for a text/chat API supporting all features introduced in 1.7 and later:
https://github.com/Bukkit/Bukkit/pull/1111

Added integration to ````Title````API.
This API is also meant to be used with other features introduced in 1.8 (signs, books...).

All authors gave permission to relicence it under MIT.

Due to a lack of matching classes i copy/pasted it just yet.
Any suggestions for improvements?

**PR Breakdown:**

This PR adds a builder interface based on a ````Message```` to which you append ````MessagePart````s to build a rich chat message containing (or not):

* a ````TextFormatting```` compatible text, a localized text, an ````Entity```` name, an ````ItemStack```` name or an ````Achievement```` name ;
* an optional ````TextHover```` text (showing a multi-color multi-line text, an ````Achievement```` description, an ````Entity```` description or an ````ItemStack```` description) ;
* an optional ````TextClickAction```` (executing commands / sending chat message, proposing commands / proposing chat message, or opening urls (actually opens the prompt), ...).

These messages handle colors and formatting using ````TextFormatting```` just like standard messages.

Many (many) shortcuts have been added to ````Message```` to make it easier to append specific elements, see ````Message```` static constructors, append methods and insert methods.

**Authors:**
* @bendem did a lot of things
* @Ribesg did a lot of things
* @ST-DDT did a lot of things