Add MultipleStringTemplateCalculator to calculate several strings at once

[tmteam]

For example we got some layout in some form

Dashboard text:  'Hello {name}. Current value is {x}'
Button1 text:  'Increase value to {x+1}'
Button2 text:  'Decrease value to {x-1}'

'x' - is shared variable among all three text expression.

It is equal to such nfun script:

d =  'Hello {name}. Current value is {x}'
b1 =  'Increase value to {x+1}'
b2 =  'Decrease value to {x-1}'

Current api does not allow us to share variable 'x' in such a way.