[ML][Pipeline] GetSource implementation

[ML][Pipeline] GetSource implementation

ACR: TWDAPI-274

[Verification] Code compiles without error. Tested in chrome console.

var pipeline = tizen.ml.pipeline.createPipeline("appsrc name=appsrc ! other/tensor,dimension=(string)4:1:1:1, type=(string)uint8,framerate=(fraction)0/1 ! tensor_if name=tif compared-value=CUSTOM compared-value-option=tif_custom_cb_name ")
var source = pipeline.getSource("appsrc")
var tensor = source.inputTensorsInfo

Change-Id: I3c09d2f91758c19e82ade9e6e5237ddc0a8ef76e
Signed-off-by: Lukasz Bardeli <l.bardeli@samsung.com>