first phase of spider cleanup

first phase of spider cleanup

Original commit message from CVS:
first phase of spider cleanup
- get rid of the buffer cache for type finding
- do type finding within spider identity instead of in seperate element
- currently doing type finding with the first buffer only. will eventually merge buffer until there is "enough" data to typefind with
- spider now only has 1 sink instead of many. I don't believe it would be possible to mux with spider anyway
- if type finding fails, gst_element_error is called. Its up to the app to catch the error signal and stop the pipeline