Handle DownloadManager expceptions

Handles illegal state exceptions thrown by DownloadManager
on two ocassions:
* the directory sdcard/Downloads is an ordinary file
* could not create dirctory sdcard/Downloads

Change will log an error, additionally toast with information
will pop up.

Change-Id: If853d3218a188bc77c187362a70697126b90989d
Merge branch 'cm-11.0' of git://github.com/CyanogenMod/android_packages_apps_Browser into cm-11.0
Merge branch 'cm-11.0' of https://github.com/temasek/android_packages_apps_Browser into HEAD