Whisk Client Refactor including Platform Agnostic Home Dir location

After go client is upgraded to use platform independent library to determine the home directory (see issue # https://github.com/apache/incubator-openwhisk-client-go/issues/108), update whisk deploy to adopt those changes.

Also, @mrutkows and I discovered there is a discrepancy in initializing and creating whisk client object in whisk deploy. There are calls in multiple places which overrides the previous calls.

`initConfig` at https://github.com/apache/incubator-openwhisk-wskdeploy/blob/master/cmd/root.go#L102 reading `.wskprops` right when whisk deploy is invoked even before reading manifest file.

Again, while deploying openwhisk assets, new whisk config object is created at https://github.com/apache/incubator-openwhisk-wskdeploy/blob/master/cmd/root.go#L223

The same object is initialized while undeployment at https://github.com/apache/incubator-openwhisk-wskdeploy/blob/master/cmd/root.go#L278 and at https://github.com/apache/incubator-openwhisk-wskdeploy/blob/master/cmd/root.go#L335

Validate whether reading `.wskprops` in `initConfig` is of any use and document what is it used for. Discard it if not needed.