fix issue when windows username contains dots

[yarix]

the windows user can contain dots which are not valid for namespace creation.
for example with user name "first.last", the setup script fails with:

Creating namespace 'first.last-dev' ...
The Namespace "first.last-dev" is invalid: metadata.name: Invalid value: "first.last-dev": a lowercase RFC 1123 label must consist of lower case alphanumeric characters or '-', and must start and end with an alphanumeric character (e.g. 'my-name',  or '123-abc', regex used for validation is '[a-z0-9]([-a-z0-9]*[a-z0-9])?')
Error while creating namespace first.last-dev.

the solution here is to replace every '.' with '-'