Fix issues with fonts on button theming, add bootstrap3 button theme

src/definitions/elements/button.less

@@ -34,6 +34,8 @@
   background-color: @backgroundColor;
   color: @textColor;
 
+  font-family: @fontFamily;
+
   margin: 0em @horizontalMargin @verticalMargin 0em;
   padding: @verticalPadding @horizontalPadding (@verticalPadding + @shadowOffset);
 

src/themes/bootstrap3/elements/button.variables

@@ -0,0 +1,63 @@
+/*-------------------
+   Button Variables
+--------------------*/
+
+/* Button Variables */
+@pageFont: Helvetica Neue, Helvetica, Arial, sans-serif;
+@textTransform: none;
+@fontWeight: normal;
+@textColor: rgba(51, 51, 51, 1);
+
+@borderRadius: 0.2857rem;
+
+@lineHeight: 1.42857;
+@verticalPadding: 0.8571em;
+@horizontalPadding: 0.8571em;
+
+@backgroundColor: @white;
+@backgroundImage: none;
+
+
+@borderBoxShadowColor: rgba(0, 0, 0, 0.14);
+
+@green: #5CB85C;
+@red: #D9534F;
+@blue: #337AB7;
+@green: #60B044;
+@orange: #F0AD4E;
+
+@primaryColor: @blue;
+@secondaryColor: @green;
+
+@labeledIconBackgroundColor: transparent;
+
+@basicBorderSize: 0px;
+@basicColoredBorderSize: 0px;
+@invertedBorderSize: 0px;
+
+@basicActiveBackground: transparent;
+@basicHoverBackground: transparent;
+@basicDownBoxShadow:
+  0px 0px 0px 1px #ADADAD inset,
+  0 3px 5px rgba(0, 0, 0, 0.125) inset
+;
+
+@groupButtonOffset: 0px 0px 0px -1px;
+@verticalGroupOffset: 0px 0px -1px 0px;
+
+/* States */
+
+@hoverBackgroundColor: #E6E6E6;
+@hoverBoxShadow:
+  0px 0px 0px 1px #ADADAD inset
+;
+
+@downBackgroundColor: #E6E6E6;
+@downBoxShadow:
+  0px 0px 0px 1px #ADADAD inset,
+  0 3px 5px rgba(0, 0, 0, 0.125) inset
+;
+
+@activeBackgroundColor: #E6E6E6;
+
+@disabledOpacity: 0.65;

src/themes/default/elements/button.variables

@@ -18,6 +18,7 @@
 /* Text */
 @textTransform: none;
 @tapColor: transparent;
+@fontFamily: @pageFont;
 @fontWeight: bold;
 @textColor: rgba(0, 0, 0, 0.6);
 @textShadow: none;