fix(android-upload): Fix some params vars to be a string

[romulowspp]

PR Checklist

• [X] The PR title follows our guidelines: https://github.com/NativeScript/NativeScript/blob/master/CONTRIBUTING.md#commit-messages.
• [X] There is an issue for the bug/feature this PR is for. To avoid wasting your time, it's best to open a suggestion issue first and wait for approval before working on it.
• [X] All existing tests are passing
• [X] Tests for the changes are included

What is the current behavior?

When the parameter payload has a type that isn't a string it throws one Java Exception about wrong type passed to method.

What is the new behavior?

Now you i convert all types in parameter value and name to string.

Fixes #249 .

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[romulowspp]

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[romulowspp]

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