Don't ignore the minSDKVersion preference from config.xml

Use the correct minSdkVersion comparing with the preference from config.xml.
Add the option of "--variable XWALK_MULTIPLEAPK=false" if build the architectures
in one apk.

platforms/android/xwalk.gradle

@@ -29,13 +29,6 @@ repositories {
   }
 }
 
-if (cdvBuildMultipleApks == null) {
-    ext.cdvBuildMultipleApks = true
-}
-if (cdvMinSdkVersion == null) {
-    ext.cdvMinSdkVersion = 14
-}
-
 def getConfigPreference(name) {
     name = name.toLowerCase()
     def xml = file("res/xml/config.xml").getText()
@@ -56,6 +49,14 @@ def getConfigPreference(name) {
     return ret ? ret : defaultValue
 }
 
+if (cdvBuildMultipleApks == null) {
+    ext.cdvBuildMultipleApks = getConfigPreference("xwalkMultipleApk").toBoolean();
+}
+if (cdvMinSdkVersion == null) {
+    def minSdk = getConfigPreference("android-minSdkVersion");
+    ext.cdvMinSdkVersion =  minSdk && minSdk.toInteger() > 14 ? minSdk : 14;
+}
+
 if (!project.hasProperty('xwalkMode')) {
     def mode = getConfigPreference("xwalkMode")
     println mode

plugin.xml

@@ -23,6 +23,7 @@
             <preference name="xwalkVersion" default="14+"/>
             <preference name="xwalkCommandLine" default="--disable-pull-to-refresh-effect"/>
             <preference name="xwalkMode" default="embedded" />
+            <preference name="xwalkMultipleApk" default="true" />
         </config-file>
 
         <config-file target="AndroidManifest.xml" parent="/*">