Dev: multi-table support & fixes

[Chenglong-MS]

• support adding more tables to data formulator (and deleting unneeded ones)
• fix various issues related to load file / import session
• fix some layout issue on data threads

[Chenglong-MS]

@noless3011 would you like to take a look and test out this version?

[noless3011]

I import 2 table orders.csv and products.csv and formulate 1 chart for each table. The first one have no problem but in the second table, I think it use the data from table 1 to create the chart so it failed.

[noless3011]

Btw, this is the columns of both table

• orders: order_id,customer_id,order_status,order_date,required_date,shipped_date,store_id,staff_id
• products: product_id,product_name,brand_id,category_id,model_year,list_price

[Chenglong-MS]

@noless3011 yep, that's bug. Hopefully it is fixed now? If it works I would merge it to main.

Would like to test on:

1. single table formulation still works
2. now it's possible to drag and drop fields from different tables to allow data formulator to join multiple uploaded tables.

here is an example of asking data formulator to combine wheat production (wheat.csv) and monarch (from a second Monarch table) to visualize them together:

multi-table-demo.mov

[noless3011]

I have been using it for a couple of hours but found no errors.
I think there could be a separator for different tables in the derive new concept -> derive from fields menu