Start moving colors into themes

Using attrs instead of fixed colors it will be possible to style
everything and also dynamically grab the color where needed in code.
This is done with colorEmphasis as an initial test.

Also remove several unused colors.

OpenKeychain/src/main/res/layout/api_app_settings_activity.xml

@@ -117,7 +117,7 @@
         android:layout_height="wrap_content"
         android:elevation="4dp"
         fab:fab_icon="@drawable/ic_play_arrow_white_24dp"
-        fab:fab_colorNormal="@color/fab"
-        fab:fab_colorPressed="@color/fab_pressed" />
+        fab:fab_colorNormal="?attr/colorFab"
+        fab:fab_colorPressed="?attr/colorFabPressed" />
 
-</RelativeLayout>
+</RelativeLayout>

OpenKeychain/src/main/res/layout/drawer_custom_header.xml

@@ -4,7 +4,7 @@
     android:layout_width="match_parent"
     android:layout_height="match_parent"
     android:gravity="center"
-    android:background="@color/primary">
+    android:background="?attr/colorPrimary">
 
     <TextView
         android:layout_width="wrap_content"
@@ -13,4 +13,4 @@
         android:text="@string/app_name"
         android:textColor="@color/white"
         android:layout_gravity="center_horizontal" />
-</LinearLayout>
+</LinearLayout>

OpenKeychain/src/main/res/layout/key_list_fragment.xml

@@ -45,8 +45,8 @@
         android:layout_alignParentRight="true"
         android:layout_alignParentEnd="true"
         android:layout_alignParentBottom="true"
-        fab:fab_addButtonColorNormal="@color/primary"
-        fab:fab_addButtonColorPressed="@color/primary_dark"
+        fab:fab_addButtonColorNormal="?attr/colorPrimary"
+        fab:fab_addButtonColorPressed="?attr/colorPrimaryDark"
         fab:fab_addButtonSize="normal"
         fab:fab_addButtonPlusIconColor="@color/icons"
         fab:fab_expandDirection="up"
@@ -61,8 +61,8 @@
             android:layout_width="wrap_content"
             android:layout_height="wrap_content"
             fab:fab_icon="@drawable/ic_qrcode_white_24dp"
-            fab:fab_colorNormal="@color/primary"
-            fab:fab_colorPressed="@color/primary_dark"
+            fab:fab_colorNormal="?attr/colorPrimary"
+            fab:fab_colorPressed="?attr/colorPrimaryDark"
             fab:fab_title="Scan QR Code"
             fab:fab_size="mini" />
 
@@ -71,8 +71,8 @@
             android:layout_width="wrap_content"
             android:layout_height="wrap_content"
             fab:fab_icon="@drawable/ic_cloud_search_24dp"
-            fab:fab_colorNormal="@color/primary"
-            fab:fab_colorPressed="@color/primary_dark"
+            fab:fab_colorNormal="?attr/colorPrimary"
+            fab:fab_colorPressed="?attr/colorPrimaryDark"
             fab:fab_title="Search Cloud"
             fab:fab_size="mini" />
 
@@ -81,10 +81,10 @@
             android:layout_width="wrap_content"
             android:layout_height="wrap_content"
             fab:fab_icon="@drawable/ic_folder_white_24dp"
-            fab:fab_colorNormal="@color/primary"
-            fab:fab_colorPressed="@color/primary_dark"
+            fab:fab_colorNormal="?attr/colorPrimary"
+            fab:fab_colorPressed="?attr/colorPrimaryDark"
             fab:fab_title="Import from File"
             fab:fab_size="mini" />
 
     </com.getbase.floatingactionbutton.FloatingActionsMenu>
-</RelativeLayout>
+</RelativeLayout>

OpenKeychain/src/main/res/layout/view_key_activity.xml

@@ -200,7 +200,7 @@
         tools:visibility="visible"
         android:elevation="4dp"
         fab:fab_icon="@drawable/ic_qrcode_white_24dp"
-        fab:fab_colorNormal="@color/fab"
-        fab:fab_colorPressed="@color/fab_pressed" />
+        fab:fab_colorNormal="?attr/colorFab"
+        fab:fab_colorPressed="?attr/colorFabPressed" />
 
-</RelativeLayout>
+</RelativeLayout>