Add cooldown time

[1470429149]

I think this is a very necessary feature and we should add a global cooldown
When players use a cheat client, repeatedly clicking on a single menu will take up a lot of server resources.

[BlitzOffline]

Having cooldowns built into DeluxeMenus is not a bad idea.

Notes:

• Built-in cooldowns should be ephemeral (persist until the plugin is unloaded)
• Should be one of the first validations done
• Should be global, per menu and item
• Should have a maximum value (suggestion: 3600 seconds / 72000 ticks)
  People who want longer cooldowns should use existing solutions such as MasterCooldowns or temporary permissions.

Temporary solution

How to create cooldowns using MasterCooldowns:

1. Start by creating a requirement (view/click/open)

requirements:
  cooldown:
    type: string equals
    input: '%mcd_isinactive_COOLDOWN-ID%'
    output: 'Yes'
  deny_commands:
  - '[message] &cTry again in %mcd_left_formatted_COOLDOWN-ID%, you are on cooldown!'

2. Add the cooldown (e.g. on click)
   [console] mcd add %player_name% COOLDOWN-ID duration

This is not the only way to create cooldowns for DM, temporary permissions being another example.