pin: Use less margin

Introduce a common.css so styles don't deviate unintentionally between
the different themes. Way more stuff can be moved here once this is in.

data/common.css

@@ -0,0 +1,6 @@
+/* Theme independent style */
+
+sq_view.pin sq_button {
+    border-radius: 0px;
+    margin: 1px 1px 1px 1px;
+}

data/squeekboard.gresources.xml

@@ -1,6 +1,7 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <gresources>
   <gresource prefix="/sm/puri/squeekboard">
+   <file compressed="true">common.css</file>
    <file compressed="true">style.css</file>
    <file compressed="true">style-Adwaita:dark.css</file>
    <file compressed="true" preprocess="xml-stripblanks">popup.ui</file>

data/style-Adwaita:dark.css

@@ -58,3 +58,5 @@ sq_button.small {
     background: #1c71d8;
     border-color: #3584e4;
 }
+
+@import url("resource:///sm/puri/squeekboard/common.css");

data/style.css

@@ -61,3 +61,5 @@ sq_button.small {
     background: mix(@theme_selected_bg_color, @theme_bg_color, 0.4); /*#1c71d8;*/
     border-color: @borders; /*#3584e4;*/
 }
+
+@import url("resource:///sm/puri/squeekboard/common.css");