#942 NYC-1956 Signal mast files corrections

[John Lang]

1) Update to the NYC-1956 signal files. I had left out the hyphen to the name NYC-1956 in the reference to the aspect table in some of the appearance files. This resulted in a different aspect table showing up when editing signal masts in the signal mast table. I also changed a couple of the aspect mappings to better reflect certain signal indications.
2) Edited the index.shtml file in the root of the signals folder that now includes the listing for the NYC-1956 signals when viewing what is on the local machine when viewed through the web interface.

[John Lang]

Index shtml

[Bob Jacobsen]

Thanks! Will be in JMRI 3.7.1