Platform Agnostic - determine home dir location

[pritidesai]

@jthomas discovered wskdeploy was looking for .wskprops file under current directory instead of user's home for 386 version of OS (apache/openwhisk-wskdeploy#1014).

@mrutkows applied a quick fix to unblock @jthomas so that he can continue working on his presentation (apache/openwhisk-wskdeploy#1015).

But in long term, we would like to fix this in right way which is adding it in Go client so that the same functionality can be used by the CLI and also by Whisk Deploy.

We are looking at changing GetPropsFromWskprops located at https://github.com/apache/incubator-openwhisk-client-go/blob/master/whisk/wskprops.go#L162

Add functionality of reading .wskprops path using homedir.Expand() like it done in CLI at https://github.com/apache/incubator-openwhisk-cli/blob/461f94fafe405feb3c664a43f6c117bac4d3c27f/commands/property.go#L402.

After the go client is changed, we need to update Whisk Deploy and CLI to use this functionality from here.