Changes to allow past date selection, plus various other improvements/clean up

[atironati]

This pull request does a lot of things, which will be detailed below (in detail) once I feel like it

• Allows selection of dates in the past by implementing a hash-based representation of months in the calendar
• Adds highlighting to input of active date selector (start/end)
• Switches colors of start and end date representations, because I believe green is better suited as a start date identifier
• Adds the start-end-date.gif as a base-64 encoded image in the css, so users don't have to worry about copying over the image into their projects
• Cleans up some unused/extraneous code

Edit: Feel free to tear my work apart, I'm sure this is ripe for the jinging

[atironati]

I put this file in the pr just so you could see how I configured calendeer for CM2, and to see if you thought any of this stuff should just be added to calendeer itself