Group binding

[ryukzak]

Add new type of synthesis decision: Binds, which contain a set of simple bind the following form:

    | GroupBind {isObliviousBinds :: Bool, bindGroup :: M.Map tag [F v x]}

With the following metrics to estimate quality of decision:

    | GroupBindMetrics
        { pOnlyObliviousBinds :: Bool
        -- ^ We don't have alternatives for binding
        , pFunctionPercentInBinds :: Float
        -- ^ number of binded functions / number of all functions in DFG
        , pAvgBinds :: Float
        -- ^ average number of binds per unit
        , pVarianceBinds :: Float
        -- ^ variance of binds per unit
        , pAvgUnitWorkload :: Float
        -- ^ average number of variables after bind per unit
        , pVarianceUnitWorkload :: Float
        -- ^ variance of variables after bind per unit
        }

Be aware about some naming refactoring:

• Bind -> SingleBind
• BindDecisionView -> SingleBindView
• BindMetrics -> SingleBindMetrics
• Reworked TreeInfo fields.

[ryukzak]

Future work: #255

[iburakov]

Based on a quick glance, LGTM, just a typo and a question