add minsdkversion to spell checker sample

and more info to html page

Change-Id: Icbd492e61c14f78d52d731c16c55620e9b5adc7d

samples/SampleSpellCheckerService/AndroidManifest.xml

@@ -19,6 +19,7 @@
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
     package="com.example.android.samplespellcheckerservice" >
 
+    <uses-sdk android:minSdkVersion="14"/>
     <application
         android:label="@string/app_name" >
         <service

samples/SampleSpellCheckerService/_index.html

@@ -1,3 +1,5 @@
 <p>A sample showing how to create a spell checker with the <code><a
 href="../../../reference/android/service/textservice/SpellCheckerService.html">SpellCheckerService</a></code>
 APIs introduced in Android 4.0 (API level 14).</p>
+<p>This app does not have a launcher activity. Once you install it, go to the system's input settings and enable
+"Sample correction" as the spelling correction service. </p>