Updated Queuing Mechanism

[clackner-gpa]

This updates the Queueing Mechanism to queue multiple Downloaders at once.

Updates to the OperationsController will result in a single call with the list of targets as POST request.
Updates to Servicehost include better allocation of acronyms to individual polling nodes and a 1 second debounce on scheduled Tasks coming from a Meter based Schedule so they get queued all at once.

Added Logging of Queue Distribution to remote nodes.
Added endpoint to get health summary for openMIC

The following DB changes are needed:

CREATE TABLE NodeCheckin
(
    ID INT IDENTITY(1, 1) NOT NULL PRIMARY KEY,
    URL VARCHAR(200) NOT NULL,
    LastCheckin DATETIME2 NOT NULL,
    FailureReason VARCHAR(MAX) NULL,
    TasksQueued INT NOT NULL DEFAULT 0,
    CONSTRAINT IX_NodeCheckin_URL UNIQUE (URL ASC)
)
GO

Still missing:
Added visibility for SystemCenter to show Trigger Service notification