Update README.bsd, mainly to put just the primary dependencies that
Wireshark needs and remove the others since GTK2/GTK3/Qt require
different things and those may change over time so let those programs
tell the user what they need.

Change-Id: I64d038564f6151d4a46d986e677f2cdc13ff87f2
Reviewed-on: https://code.wireshark.org/review/6028
Reviewed-by: Stephen Fisher <sfisher@sdf.org>