Add a changelog generator helper script

ps2: switch a remnant of my personal script setup to be android_build_top-relative
ps3: remove humorous digs at the author of the commit I just 'opened up a can on'
ps4: accumulate date-stamped changelogs in a directory in repo root
ps5: cleanup whitespace
ps6: aaand done

Change-Id: Ieffabf5a8dd58d8c803b20c1cda0cbe79fb33ef4
Signed-off-by: nuclearmistake <nuclearmistake@gmail.com>