add two apis: gst_element_connect_elements_many (elem1, elem2, ...)

add two apis: gst_element_connect_elements_many (elem1, elem2, ...)

Original commit message from CVS:
* add two apis:
* gst_element_connect_elements_many (elem1, elem2, ...)
- calls gst_element_connect_elements() in order
- should be called gst_element_connect_many, but we need to rename gst_element_connect_elements first
- simplifies common-case code
* gst_bin_add_many (bin, elem1, ...)
- calls gst_bin_add on all of the elems
- again, simplifying common code