gst1-plugins-bad: cleanup of build options

gst1-plugins-bad: cleanup of build options

Remove non-existing options:
 * --disable-wsap
 * --disable-direct3d
 * --disable-gsettings

Remove options that are already handled later in the .mk file, using
optional dependencies:
 * --disable-rtmp
 * --disable-hls
 * --disable-dash

Rename disable->strp to disable-srtp, which essentially fixes a typo.

Remove liveadder plugin - no longer a separate built option, it's been
merged into audiomixer. Config.in.legacy handling is added for the
removed option.

Signed-off-by: Marcin Nowakowski <marcin.nowakowski@imgtec.com>
[Thomas: add Config.in.legacy handling for the liveaddr plugin option,
tweaks to the commit log.]
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>