Add initial version of the unit info window.

DCS features a massive range of aircraft and land vehicles, and not all of them make their role(s) clear just from the name alone. What this commit does is add an "information" button (and resultant window) to the recruitment section. This should allow new players to understand what each unit is/does.

Current state - every aircraft has a country of origin and an introduction date for that variant. Some also have a small placeholder description, taken from ED's store page for that aircraft. There is also a placeholder picture (taken from a rejected image from my own personal photography) that will, in time, show a banner image of each unit.

Todo - add appropriate screenshots for each aircraft's banner, replace the placeholder text for each aircraft (this will take a while...) and add more data points for each unit type, such as a unit role (i.e. "air-superiority fighter", "multirole fighter", etc) or perhaps a list of weapons carried. I also haven't made a start on the huge number of ground units yet.

resources/stylesheets/style-dcs.css

@@ -179,6 +179,21 @@ QPushButton[style="btn-sell"]:hover{
     background:#D84545;
 }
 
+/* Info button */
+QPushButton[style="btn-info"]{
+    background-color:#329E9E;
+    color: white;
+    border-radius:2px;
+    font-weight:bold;
+    text-transform:lowercase;
+    margin: 0px;
+    padding: 2px;
+}
+
+QPushButton[style="btn-info"]:hover{
+    background:#45D8D8;
+}
+
 
 
 QPushButton[style="btn-danger"]{
@@ -300,6 +315,18 @@ QLabel[style="SEAD"]{
     padding:2px 6px;
 }
 
+QLabel[style="info-element"]{
+    border: 1px solid #435466;
+    color:white;
+    padding:2px 6px;
+}
+
+QTextBrowser[style="info-desc"]{
+    border: 1px solid #435466;
+    color:white;
+    padding:2px 6px;
+}
+
 /*QGroupBox these are the sections that look like fieldsets*/
 QGroupBox {
     margin-top: 1ex; /* leave space at the top for the title */