Vendor: Implement ad blocker [1/3]

*Picked from Dirty Unicorns
*This uses two prebuilt hosts files and switches between them by symlinking

PS2: Commit msg
PS3: Add a big ass hosts file from 4 default Adaway sources
PS4: Remove lines starting with '#' because they will be ignored anyways. Also decreases file size a bit.

Change-Id: Ia12047af9882feac86bfde2f7d1602946c66cbe0