fix: refine sidebar selection and vertically center file text

Remove left border from selection to avoid competing with git markers,
use flat rgba blue fill only. Fix 1px vertical text offset in working
set file items.

Author: abose

src/styles/brackets.less

@@ -1447,7 +1447,7 @@ a, img {
         height: 16px;
         line-height: 15px;
         margin-left: 18px;
-        padding: 3px 0 3px 0;
+        padding: 4px 0 3px 0;
 
         cursor: default;
 
@@ -1469,9 +1469,8 @@ a, img {
 
 .sidebar-selection, .filetree-selection {
     background: @bc-sidebar-selection;
-    border-top: none;
-    border-bottom: none;
-    border-left: none;
+    border: none;
+    box-shadow: none;
     box-sizing: border-box;
     height: 23px;
     width: 100%;