Feature Request : az functionapp creation with SSH Keys

**Description**

Feature Request: Currently, to deploy a function app via az functionapp deployment source config the function app needs to be using HTTPS endpoint. To support using SSH Keys present under AZ CLI, would it be possible to add functionality to pull the SCM using SSH Keys from likes of bitbucket, github, TFS SCM like this:

```
az functionapp deployment source config --name $functionapp \
--resource-group myResourceGroup \
--repo-url git@github.com:Azure-Samples/functions-quickstart.git \
--branch master --location \
--manual-integration
```

### Environment summary

Install Method (e.g. pip, interactive script, apt-get, Docker, MSI, edge build) / CLI version (`az --version`) / OS version / Shell Type (e.g. bash, cmd.exe, Bash on Windows) - Bash - Azure on cloud
```
myuser@Azure:~$ az --version
azure-cli (2.0.21)

acr (2.0.15)
acs (2.0.19)
appservice (0.1.20)
backup (1.0.3)
batch (3.1.7)
batchai (0.1.3)
billing (0.1.6)
cdn (0.0.10)
cloud (2.0.10)
cognitiveservices (0.1.9)
command-modules-nspkg (2.0.1)
component (2.0.8)
configure (2.0.12)
consumption (0.1.6)
container (0.1.13)
core (2.0.21)
cosmosdb (0.1.15)
dla (0.0.15)
dls (0.0.18)
eventgrid (0.1.5)
extension (0.0.6)
feedback (2.0.6)
find (0.2.7)
interactive (0.3.11)
iot (0.1.14)
keyvault (2.0.14)
lab (0.0.13)
monitor (0.0.12)
network (2.0.18)
nspkg (3.0.1)
profile (2.0.15)
rdbms (0.0.9)
redis (0.2.10)
reservations (0.1.0)
resource (2.0.18)
role (2.0.14)
servicefabric (0.0.6)
sql (2.0.15)
storage (2.0.19)
vm (2.0.18)

Python location '/opt/az/bin/python3'
Extensions directory '/home/myuser/.azure/cliextensions'

Python (Linux) 3.6.1 (default, Nov 10 2017, 16:23:17)
[GCC 4.8.4]

Legal docs and information: aka.ms/AzureCliLegal

myuser@Azure:~$
```