Unit group data would be stored in datatable

Unit group datatable keys would be:

- primary key f.i.: 1

- name code: f.i. $Length or $Area, code for localization

- type of unit group:
0: one unit type and one base unit f.i. area tab
1: 2 independent unit type and 2 base units on the same tab
2: 2 unit types linked by a fix value f.i. length+frequency; 1 base unit
3: 2 unit types linked by a variable value f.i. viscosity; 1 base unit
4: 3 independent unit types and 3 base units f.i. concentration tab

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- Name code of first unit type f.i.: $Dynamic_viscosity

- Name code of second unit type f.i.: $Kinematic_viscosity

- Name code of third unit type f.i.: $Mole_per_volume