ace fold widget arrows should show on heighcontrast mode #heighcontrast

[mkassaei]

The 'ace fold widget' which uses arrow icons that allow users to expand and collapse a chunk of code such as functions/methods, ..., is very confusing for users in high contrast mode, because the arrow icons do not show (e.g. IE11 in high contrast mode).

After the result of our accessibility testing at the OU, I have done some CSS changes so that users in high contrast mode have the similar experience.

To start with I have put the css changes within
@media screen and (-ms-high-contrast: active) {
.....
}
However, we then decided to get rid of the browser specific tag and therefore tried to replicate the existing arrow icons with symbols and they look very similar to the original icons.

BTW, sorry about the misspelling of high contrast in the commit and branch name.