Add color themes to CSS file generation

[jpfiset]

Add the means to replace portion of the generated CSS files given a properties file.

Nunaliit offers a large set of CSS instructions, out of the box, to make a default atlas generated from it work with a certain amount of useful functions. Visual layouts and colourings are crucial parts to make the atlas work.

However, modifying the CSS thus acquired is not always easy. This is because there are numerous values used in the CSS that are identical, but used in different ways. One can not simply perform a search/replace method on CSS values since one would inevitably change values that are out of scope.

Instead of creating a stock CSS for Nunaliit with "values", I propose instead to insert names for those values and associate each name with a value in a property file. At generation, the names in the CSS are replaced with the values.

.n2help_dialog .ui-dialog-titlebar {
	background: {{header.background}};
	color: {{header.color}};
	font-family: helvetica, sans-serif;
	font-weight: 500;
}

Property file:

header.background: #3a3a3a
header.background.button: #2f2f2f
header.background.hover: #1f1f1f
header.background.selected: #160E7D
header.background.module: #444444
header.color: #fff
header.border.color: rgba(255,255,255,0.6)
header.border.color.module: #575757
header.border.button.color: #838383