PlaceholderAPI support

[mdcfe]

Just some brief notes on what would need to be done to support PlaceholderAPI.

• We probably don't want to softdepend PAPI, as I can foresee plugins breaking if we create a dependency loop by mistake.
  • Instead, we should wait for it to be enabled and when it is, we can then enable PAPI support in EssentialsX and EssentialsX Chat.
• EssentialsX will need to support PAPI both in text-loading classes and in I18n.
• EssentialsX Chat will need to support PAPI in its chat listener.

[Banbeucmas]

#1944
Althought I added Placeholder API as a soft dependency, I have done the 4th requirement, will do some more work this week.

@drtshock Did mention that creating an Utils for it should be better. I don't know if my approach to his idea is right.

This would be really helpful to server owners if this gets implemented. I've been trying to have a sound play when you get /msged, but EssX is just not playing nice with ChatInjector.

[accLarson]

PlaceholderAPI support in Kits name: and lore: etc would be great!

[LcyDev]

PlaceholderAPI support in motd.txt, info.txt, rules.txt, custom.txt, help.txt would be awesome, im currently needing that.
Also adding all tags to them, {TEAMPREFIX} {PREFIX} {TEAMSUFFIX} {SUFFIX}, etc. would be very useful too.

Seconding Conall's thoughts. The lack of support for PlaceholderAPI really stings me.