What directory should the Android webapp default to creating an annex in?

Same as the desktop webapp, users will be able to enter a directory they
want the first time they run it, but to save typing on android, anything
that gets enough votes will be included in a list of choices as well.

[[!poll open=yes expandable=yes 68 "/sdcard/annex" 6 "Whole /sdcard" 7 "DCIM directory (photos and videos only)" 2 "Same as for regular git-annex. ~/annex/"]]
