ui: Added shortcuts for navigating to next and previous reference in code view

* Added new class QtCodeNavigator between QtCodeView and QtCodeFileList that handles active ids and navigation
* Pass all files as initially collapsed to code view and decide in QtCodeNavigator which ones show content
* Rewrote requesting of active snippet display to top down approach
* Display other locations focused when active location changes
* Show corresponding edges when navigating references

bin/app/data/color_schemes/bad_rainbow.xml

@@ -167,6 +167,9 @@
 						<fill>#C2AFEF</fill>
 						<text>#3D3D3D</text>
 					</normal>
+					<focus>
+						<fill>#987CEA</fill>
+					</focus>
 				</fulltext>
 			</selection>
 		</snippet>

bin/app/data/color_schemes/bright.xml

@@ -165,6 +165,9 @@
 						<fill>#C7C7E2</fill>
 						<text>#000000</text>
 					</normal>
+					<focus>
+						<fill>#ABABDD</fill>
+					</focus>
 				</fulltext>
 			</selection>
 		</snippet>

bin/app/data/color_schemes/dark.xml

@@ -186,6 +186,10 @@
 						<fill>#207EA8</fill>
 						<text>#F7F7F7</text>
 					</normal>
+					<focus>
+						<border>#006D93</border>
+						<fill>#134B63</fill>
+					</focus>
 				</fulltext>
 			</selection>
 		</snippet>

bin/app/data/gui/code_view/code_view.css

@@ -1,4 +1,4 @@
-#code_file_list_base, #code_file_list {
+#code_container, #code_file_list {
 	background-color: <color:code/background>;
 }