Update microservice.R for supporting jsonData input in R

[LueJian]

Update functions in microservie.R to support "jsonData" input format like Python wrapper.

What this PR does / why we need it:
In R, we can use SeldonMessage with not only ndarray format, but also jsonData fromat now!
An example of "jsonData" input format : {"jsonData":{"key1":value1, "key2":value2}}

Which issue(s) this PR fixes:

Fixes #

Extending the concept from #595, supporting other language wrappers - R wrapper.

Special notes for your reviewer:
[Example] Testing it with a simple transformer-input component, just returning input as its output.

Does this PR introduce a user-facing change?:

None

[seldondev]

Hi @LueJian. Thanks for your PR.

I'm waiting for a SeldonIO member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

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[seldondev]

[APPROVALNOTIFIER] This PR is NOT APPROVED

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To complete the pull request process, please assign ryandawsonuk
You can assign the PR to them by writing /assign @ryandawsonuk in a comment when ready.

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[LueJian]

/assign @cliveseldon

[ryandawsonuk]

/lgtm
/approve

[axsaucedo]

/ok-to-test

[seldondev]

Mon Oct 19 15:42:05 UTC 2020
The logs for [lint] [2] will show after the pipeline context has finished.
https://github.com/SeldonIO/seldon-core/blob/gh-pages/jenkins-x/logs/SeldonIO/seldon-core/PR-2544/2.log

impatient try
jx get build logs SeldonIO/seldon-core/PR-2544 --build=2

[seldondev]

Mon Oct 19 15:42:15 UTC 2020
The logs for [pr-build] [1] will show after the pipeline context has finished.
https://github.com/SeldonIO/seldon-core/blob/gh-pages/jenkins-x/logs/SeldonIO/seldon-core/PR-2544/1.log

impatient try
jx get build logs SeldonIO/seldon-core/PR-2544 --build=1