Create abstract table display

[MaHaWo]

• creates a searchable table component with cells optionally being colored to indicate status
• create components for header and body of the table
• add some unit tests for internal javascript logic using svelte-testing
• fix a few minor errors
• added only minimal styling since I'm not yet sure how the whole thing will turn out when it is bound together.

resolves #4

[lkeegan]

looks nice! The filtering might be useful for admin views later. I guess a simple feature we still need here is for users to be able to click on one of the cells of this table to continue filling in that survey