tools/: cleanup man-pages, remove reference to gst-register, document env-vars

Original commit message from CVS:
* tools/README:
* tools/gst-feedback.1.in:
* tools/gst-inspect.1.in:
* tools/gst-launch.1.in:
* tools/gst-md5sum.1.in:
* tools/gst-typefind.1.in:
* tools/gst-xmlinspect.1.in:
* tools/gst-xmllaunch.1.in:
cleanup man-pages, remove reference to gst-register, document env-vars
9 files changed