XWIKI-8394: Workspace owner and initial members not set as members (nor in admin group) when the workspace identifier contains an underscore
- Removed from the Workspace API's create workspace method the first parameter (workspaceName), expecting that the workspace name be set inside the XWikiServer parameter using the setWikiName method
- Better JS validation of the workspace identifier, allowing to use only alphanumerical characters
- Minor codestyle cleanup in the UI's code
- Minor improvements in the UI's code