Add Holidays

[Virus5600]

Implement a Holiday field which identifies which days are holidays. This will allow insertion of "Holiday" dates within the DTR instead of leaving them blank or manually changing them. Frontend view must result to this:

Please note that the "TIANGGE DAY" should be replaced with "HOLIDAY" and should have black font color and yellow background color, resulting to this:

ALSO, ITALICIZE THE WORD. LMAO

[Virus5600]

Commit 71d4a4e, which is also the v1.2.0-beta release addressed and implemented this feature by modifying the Dragcheck utility script from DTR-Generator unto a full blown library. Similar on how to select regular work dates, you can just right-click the dates to select which of them are holidays. Some changes in the DTRG base code are also done to implement the "Holiday" row.

As the feature is already tested and deemed working, this issue will now be closed.