Binding a JSON type to a package causes a panic

In the current master version, binding a JSON type to a package causes a panic

Target manifest
```yaml
packages:
package1:
inputs:
param1:
key1: value1
key2: value2
```

error logs
```sh
./wskdeploy
panic: runtime error: comparing uncomparable type map[string]interface {}

goroutine 1 [running]:
github.com/apache/openwhisk-wskdeploy/parsers.(*YAMLParser).composePackageInputs(0xc000309ea0, 0xc000337410, 0xc0003de750, 0xc000338140, 0x42, 0xc000318d80, 0x56, 0xc0003de8a0, 0x1ff0f50, 0xc000159378, ...)
/home/travis/gopath/src/github.com/apache/openwhisk-wskdeploy/parsers/manifest_parser.go:324 +0x679
github.com/apache/openwhisk-wskdeploy/parsers.(*YAMLParser).ComposePackage(0xc000309ea0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, ...)
/home/travis/gopath/src/github.com/apache/openwhisk-wskdeploy/parsers/manifest_parser.go:420 +0x455
github.com/apache/openwhisk-wskdeploy/parsers.(*YAMLParser).ComposeAllPackages(0xc000309ea0, 0xc000337410, 0xc000360fa0, 0xc000338140, 0x42, 0x0, 0x0, 0x0, 0x0, 0x0, ...)
/home/travis/gopath/src/github.com/apache/openwhisk-wskdeploy/parsers/manifest_parser.go:297 +0x298
github.com/apache/openwhisk-wskdeploy/deployers.(*ManifestReader).InitPackages(0xc0001599f8, 0xc000309ea0, 0xc000360fa0, 0x0, 0x0, 0x0, 0x0, 0x108, 0x108)
/home/travis/gopath/src/github.com/apache/openwhisk-wskdeploy/deployers/manifestreader.go:58 +0x96
github.com/apache/openwhisk-wskdeploy/deployers.(*ServiceDeployer).ConstructDeploymentPlan(0xc000364160, 0x25, 0x0)
/home/travis/gopath/src/github.com/apache/openwhisk-wskdeploy/deployers/servicedeployer.go:187 +0x3eb
github.com/apache/openwhisk-wskdeploy/cmd.Deploy(0x1880980, 0x0, 0x0)
/home/travis/gopath/src/github.com/apache/openwhisk-wskdeploy/cmd/root.go:257 +0x3b7
github.com/apache/openwhisk-wskdeploy/cmd.RootCmdImp(0x1880980, 0x18b79a0, 0x0, 0x0, 0x0, 0x0)
/home/travis/gopath/src/github.com/apache/openwhisk-wskdeploy/cmd/root.go:51 +0x2b
github.com/spf13/cobra.(*Command).execute(0x1880980, 0xc00001e1e0, 0x0, 0x0, 0x1880980, 0xc00001e1e0)
/home/travis/gopath/pkg/mod/github.com/spf13/cobra@v1.1.3/command.go:852 +0x47c
github.com/spf13/cobra.(*Command).ExecuteC(0x1880980, 0x1, 0x1, 0xc00001e1e0)
/home/travis/gopath/pkg/mod/github.com/spf13/cobra@v1.1.3/command.go:960 +0x375
github.com/spf13/cobra.(*Command).Execute(...)
/home/travis/gopath/pkg/mod/github.com/spf13/cobra@v1.1.3/command.go:897
github.com/apache/openwhisk-wskdeploy/cmd.Execute()
/home/travis/gopath/src/github.com/apache/openwhisk-wskdeploy/cmd/root.go:65 +0xca
main.main()
/home/travis/gopath/src/github.com/apache/openwhisk-wskdeploy/main.go:26 +0x25
```

Start in parsers/manifest_parser.go at composePackageInputs, line 324, using the package-input manifest shown in the issue and run ./wskdeploy to reproduce the panic. Trace the JSON-valued input through package composition and add coverage for this manifest; done means deployment parsing no longer panics and preserves the nested input.

Written by the indexing model from the issue text.