Doc: making in-source builds the default option

Fix capitalization of the new UI string.

Change-Id: Iaf1dd279639936cb59aa658834c71a49ce1398ac
Reviewed-by: Daniel Teske <daniel.teske@digia.com>

doc/src/projects/creator-projects-settings-build.qdoc

@@ -70,6 +70,10 @@
 
     \endlist
 
+    To make in-source builds the default option for all projects, select
+    \gui Tools > \gui Options > \gui {Build & Run} > \gui General, and enter a
+    period (.) in the \gui {Default build directory} field.
+
     \section1 Starting External Processes
 
     \QC executes external processes to accomplish tasks such as building

src/plugins/projectexplorer/projectexplorersettingspage.ui

@@ -214,7 +214,7 @@
         <item>
          <widget class="QLabel" name="buildDirLabel">
           <property name="text">
-           <string>Default Build Directory:</string>
+           <string>Default build directory:</string>
           </property>
          </widget>
         </item>