Added scarpet bossbar function (#585)

docs/scarpet/api/Scoreboard.md

@@ -104,3 +104,62 @@ team_property('admin','seeFriendlyInvisibles',true)       Make all players in 'a
 team_property('admin','deathMessageVisibility','hideForOtherTeams')       Make all players in 'admin' see other admins even when invisible
 ```
 
+## `bossbar()`, `bossbar(id)`, `bossbar(id,property,value?)`
+
+Manage bossbars just like with the `/bossbar` command.
+
+Without any arguments, returns a list of all bossbars.
+
+When an id is specified, creates a bossbar with that `id` and returns the id of the created bossbar.
+Bossbar ids need a namespace and a name. If no namespace is specified, it will automatically use `minecraft:`.
+In that case you should keep track of the bossbar with the id that `bossbar(id)` returns, because a namespace may be added automatically.
+If the id was invalid (for example by having more than one colon), returns `null`.
+If the bossbar already exists, returns `false`.
+
+`bossbar('timer') => 'minecraft:timer'` (Adds the namespace `minecraft:` because none is specified)
+
+`bossbar('scarpet:test') => 'scarpet:test'` In this case there is already a namespace specified
+
+`bossbar('foo:bar:baz') => null` Invalid identifier
+
+`bossbar(id,property)` is used to query the `property` of a bossbar.
+
+`bossbar(id,property,value)` can modify the `property` of the bossbar to a specified `value`.
+
+Available properties are:
+
+* color: can be `'pink'`, `'blue'`, `'red'`, `'green'`, `'yellow'`, `'purple'` or `'white'`
+
+* style: can be `'progress'`, `'notched_6'`, `'notched_10'`, `'notched_12'` or `'notched_20'`
+
+* value: value of the bossbar progress
+
+* max: maximum value of the bossbar progress, by default 100
+
+* name: Text to display above the bossbar, supports formatted text
+
+* visible: whether the bossbar is visible or not
+
+* players: List of players that can see the bossbar
+
+* add_player: add a player to the players that can see this bossbar, this can only be used for modifying (`value` must be present)
+
+* remove: remove this bossbar, no `value` required
+
+```
+bossbar('script:test','style','notched_12')
+bossbar('script:test','value',74)
+bossbar('script:test','name',format('rb Test'))  -> Change text
+bossbar('script:test','visible',false)  -> removes visibility, but keeps players
+bossbar('script:test','players',player('all'))  -> Visible for all players
+bossbar('script:test','players',player('Steve'))  -> Visible for Steve only 
+bossbar('script:test','players',null)  -> Invalid player, removing all players
+bossbar('script:test','add_player',player('Alex'))  -> Add Alex to the list of players that can see the bossbar
+bossbar('script:test','remove')  -> remove bossbar 'script:test'
+for(bossbar(),bossbar(_,'remove'))  -> remove all bossbars
+```
+
+
+
+
+