增加了图片缩略图
Merge branch 'master' of https://github.com/huanghui6579/MyExplorer

Conflicts:
	res/layout/activity_file_list.xml
	res/layout/item_file_info.xml
	res/values-sw600dp/dimens.xml
	res/values-sw720dp-land/dimens.xml
	res/values-v11/styles.xml
	res/values-v14/styles.xml
	res/values/strings.xml
	res/values/styles.xml
	src/com/example/testfileexplorer/FileListActivity.java
	src/com/example/testfileexplorer/MainActivity.java