Add NSAttributedString support for UILabels

[ekille]

Current:
"H1": {
"fontStyle": {
"font": "primaryFontLight",
"size": 20
}
},

Desired:
"H1": {
"textColor": "blueColor",
"textAlignment": "Center",
"attributes": {
"fontStyle": {
"font": "primaryFontMedium",
"size": 22
},
"tracking": 100,
"lineSpacing": 5,
"ligature": 0
}
}