Consolidate button styles

This patchset will create consistent button styling according
to the styleguide and remove redundant button styles by creating
reusable button classes.

This patchset also implements a consistent strategy for including
icon assets. Currently, svg icons are imported as CSS background
images or inlined into the markup. Inlining an svg is preferred,
especially when used with buttons or links so the colors can
be easily changed for different states (hover, focus, disabled)
without having to request variants.
The icon provider allows us to inline svgs without cluttering
the markup. Webpack config was adjusted to use svg-inline-loader
when resolving svgs that are used by the icon provider directive.

- All svgs were optimized to remove unncessary information.
- Removed unused svg color variants
- Moved icons used by icon provider to separate directory to
  avoid Webpack parsing the files twice
- Small changes to navigation icons

Signed-off-by: Yoshie Muranaka <yoshiemuranaka@gmail.com>
Change-Id: I1ca214b74fc502e6b6e760cfee88b48110237c43
diff --git a/app/common/styles/directives/app-header.scss b/app/common/styles/directives/app-header.scss
deleted file mode 100644
index e69de29..0000000
--- a/app/common/styles/directives/app-header.scss
+++ /dev/null
diff --git a/app/common/styles/directives/app-navigation.scss b/app/common/styles/directives/app-navigation.scss
index 1e21659..79eb11e 100644
--- a/app/common/styles/directives/app-navigation.scss
+++ b/app/common/styles/directives/app-navigation.scss
@@ -8,8 +8,8 @@
   max-height: 40px;
   stroke-width: .5;
   display: block;
-  width: 40px;
-  margin: 0 auto .5em auto;
+  margin: .5em auto;
+  overflow: hidden;
   .st0 {
     fill: none;
     stroke: $white;
@@ -46,13 +46,21 @@
   li {
     margin: 0;
   }
+  > li > a,
+  > li > button {
+    height: 120px;
+  }
   //svg icons
   .nav-icon {
     @include navIcons;
+    width: 100%;
+    svg {
+      width: 36px;
+      height: auto;
+    }
   }
   .button, button, a {
     background: transparent;
-    height: auto;
     border: 0;
     color: $white;
     fill: $white;
@@ -66,16 +74,9 @@
     text-decoration: none;
     border-top: 1px solid transparent;
     border-bottom: 1px solid $darkgrey;
-    a {
-      margin-bottom: 5px;
-    }
-    span {
-      margin: 1em 0 0 0;
-      display: block;
-      font-size: .9em;
-      font-weight: 400;
-      line-height: 1rem;
-    }
+    font-weight: normal;
+    font-size: .9em;
+    line-height: 1.2;
     &:hover {
       background: $white;
       fill: $black;
diff --git a/app/common/styles/directives/confirm.scss b/app/common/styles/directives/confirm.scss
deleted file mode 100644
index e69de29..0000000
--- a/app/common/styles/directives/confirm.scss
+++ /dev/null
diff --git a/app/common/styles/directives/index.scss b/app/common/styles/directives/index.scss
index a70c007..5d9de6f 100644
--- a/app/common/styles/directives/index.scss
+++ b/app/common/styles/directives/index.scss
@@ -1,3 +1 @@
-@import "./app-header.scss";
-@import "./app-navigation.scss";
-@import "./confirm.scss";
\ No newline at end of file
+@import "./app-navigation.scss";
\ No newline at end of file