Add style to left sidebar and app header

- Updated hover, active and focus state for left sidebar menu items.
- Add style guide for top header navigation.
- Add new white color logo.
- Add focus and active state to current menu item.

Signed-off-by: Suren Neware <sneware9@in.ibm.com>
Change-Id: Ib97df4efda216f653ce0415c3f3ae9ae75bcb9cd
diff --git a/src/assets/styles/bmc/helpers/_variables.scss b/src/assets/styles/bmc/helpers/_variables.scss
index 10ac64a..ba32e3b 100644
--- a/src/assets/styles/bmc/helpers/_variables.scss
+++ b/src/assets/styles/bmc/helpers/_variables.scss
@@ -7,8 +7,10 @@
 
 // OpenBMC Custom Variables
 $responsive-layout-bp: lg;
-$header-height: 56px;
+$header-height: 48px;
 $navigation-width: 300px;
 $form-label-font-size: .875rem;
 $form-line-height: 1.25rem;
-$box-shadow: 0 0.25rem 0.75rem rgba(0, 0, 0, 0.3);
\ No newline at end of file
+$box-shadow: 0 0.25rem 0.75rem rgba(0, 0, 0, 0.3);
+$focus-transition: color 0.15s ease-in-out, background-color 0.15s ease-in-out,
+border-color 0.15s ease-in-out, box-shadow 0.15s ease-in-out;