dynappsrc: Add event and query handler fuctions
dynappsrc: Add event and query handler fuctions

Event/query handler functions are added at srcpad of dynappsrc.

Change-Id: Iaeea220c7fa22b36c9556f59423931b86ec39808
Reviewed-on: https://gpro.palm.com/30954
Reviewed-by: Wonchul Lee <9841bdbec9dbb2acc2dcaaa1dab0491399f0e464@lge.com>
Tested-by: Wonchul Lee <9841bdbec9dbb2acc2dcaaa1dab0491399f0e464@lge.com>

justinjoy/gst-plugins-lp,justinjoy/gst-plugins-lp