Add font size configuation file

Add font size configuation file

To support different variable product, font_scale.json is added.
With %config option in .spec file, the font_scale.json can be
uploaded only when there is no the font_scale.json in /etc.

In font_scale.json, there are 5 grade of font size, below.

$ cat /etc/font_scale.json
{
        "SMALL"  : -80,
        "NORMAL" : -100,
        "LARGE"  : -150,
        "HUGE"   : -190,
        "GIANT"  : -250
}

-80 means that 80% font scale of each application font size.
Each grade is mapping, below.

SYSTEM_SETTINGS_FONT_SIZE_SMALL == "SMALL" in font_scale.json value
SYSTEM_SETTINGS_FONT_SIZE_NORMAL == "NORMAL" in font_scale.json value
SYSTEM_SETTINGS_FONT_SIZE_LARGE == "LARGE" in font_scale.json value
SYSTEM_SETTINGS_FONT_SIZE_HUGE == "HUGE" in font_scale.json value
SYSTEM_SETTINGS_FONT_SIZE_GIANT == "GIANT" in font_scale.json value

Change-Id: I1fba03154630f41544dca8ef49595e9226724baf
Signed-off-by: JinWang An <jinwang.an@samsung.com>