Add [SpellInfo] and new method for [Player]

[iThorgrim]

• Add new object [SpellInfo].
• Add player:GetSpells() for getting all learned spell.
• Add [Global] GetSpellInfo(spell_entry) for getting SpelInfo with spell_entry.

[Terrorblade]

Looks fine, but you should at least NYI returns for the unsupported emulators

[Foereaper]

Like mentioned in DM's, when it comes to things like new objects we need to make sure that we can have an equivalent on the other emulators to prevent API differences getting out of hand. I think @Niam5 is probably the appropriate Mangos resource to let us know if this is possible or not, or whether something needs changing to achieve 1:1.

I would however like GetSpells to be renamed to GetKnownSpells or something similar to make it a little clearer what it actually returns.

[Foereaper]

We'll work on this PR and make sure it works with the other cores in the SpellInfoPR branch before merging into master

[iThorgrim]

I'm taking the liberty of closing this PR for the time being, as the Eluna structure is not up to date on this branch, so I'll have to update it manually.