Add module - header dropdown

[rrchai]

AC:

• ui should be one function within the dashboadHeader()
• enable to display selections when generating template and validation
• cycle back to the issue mentioned here
• refactor DCA to use this module

Note: Since the values of dropdown will interact with dropdowns in the first tab, be careful about the sequence of events changes. Otherwise, the final selections used the validation or generating template tabs will be not accurate.