srt: rework to accept connection mode by uri parameters

Submitted by Justin Kim @joykim

Link to original bug (#796701)

Description

Created attachment 372859
srt: Integrate server and client element into one

We have srt{client,server}{src,sink} elements in accordance to the
norm of the connection-oriented protocols. However, SRT connection
mode can be changed by uri parameters so it requires an integrated
element to handle the parameters.

Patch 372859, "srt: Integrate server and client element into one":
0001-srt-Integrate-server-and-client-element-into-one.patch