Add time zone selector to the New Project wizard

[alansemenov]

• Add a combobox (optional selection) for selecting a time zone for new project/layer to the language selection step of the New Project wizard (TODO: add a link describing how to fetch the list of time zones). TBD: Add a region/country selector before enabling the time zone selector?
• Pre-select an option that corresponds the current time zone
• Display selected time zone on the Summary step of the Wizard
• Pass selected time zone to admin API
• Add time zone selector to the project/layer details form (previously selected time zone can be unset)