move font-awesome to style.less from notebook-specific less

allows it to be excluded from ipython.min.css,
where it doesn't make much sense.

IPython/html/static/base/less/style.less

@@ -2,5 +2,3 @@
 @import "../base/less/mixins.less";
 @import "../base/less/flexbox.less";
 @import "../base/less/page.less";
-@import "../components/font-awesome/build/assets/font-awesome/less/font-awesome.less";
-@FontAwesomePath:    "../components/font-awesome/build/assets/font-awesome/font";

IPython/html/static/style/style.less

@@ -2,6 +2,10 @@
 @import "../components/bootstrap/less/bootstrap.less";
 @import "../components/bootstrap/less/responsive.less";
 
+// Font-Awesome
+@import "../components/font-awesome/build/assets/font-awesome/less/font-awesome.less";
+@FontAwesomePath:    "../components/font-awesome/build/assets/font-awesome/font";
+
 // base
 @import "../base/less/style.less";