Demos: Updated page sections info on intro page

Fixes gh-7052
Build: Updated AUTHORS.txt
Textinput: Correct padding-right for input with clear button

Fixes gh-7011
Closes gh-7072
Icons: Same size for all icons and center the image

Fixes gh-6356
Closes gh-7031
Icons: Alphabetise icon examples in the demos
Icons: Fixed markup and style guide issues on grunticon demo page
Button: Correction of wrong border-radius property

Fixes gh-7073
Closes gh-7074
Toolbar: Corrections in back button info on demo page

Fixes gh-6835
Closes gh-7075