Start more than one task via REST API

[mountaindude]

Accept an array (JSON format) of multiple tasks that should all be started.

• Verify that all tasks exists before starting them, report missing tasks to the caller.
• Option for failing completely if a single task doesn't exist, or start all existing tasks and report the missing ones to the caller.
• Accept several ways of identifying what tasks should be started. These should be additive, i.e. the union of tasks matching either of the options below. Array of
  • taskIds
  • tags
  • custom properties

This would require a modification of the current endpoint for starting tasks, /v4/reloadtask/{taskId}/start.
A special taskId of ´-´could be used to tell Butler that all info should be taken from the body instead of the URL.
That would also allow for future enhancements, as the body can be arbitrarily extended.