Revert "Revert "Corrected missing password error message; added tests for error messages; refactored Flash tag""

This reverts commit fa983fd235ed7a739110b773d297d97f6d846688.
Revert "Revert "Prepared Users database""

This reverts commit 1de72b5efd2fbc0770193398c2f35a8be201fc46.
Revert "Revert "Added a signin page (unfinished)""

This reverts commit 7ef7eba832ea5310744468b8a2d76eee5923cf98.
Revert "Added a signin page (unfinished)"

This reverts commit 4613bf9824046fef073eed10bbf697293855bb59.
Revert "Prepared Users database"

This reverts commit 93144bc3752158bec5b92a7c09bcb557222ab33b.
Revert "Corrected missing password error message; added tests for error messages; refactored Flash tag"

This reverts commit 06a2e10322020e92c910625165988f92a95b2503.