Refactor balances (value * PONT)

[borispovod]

Description:

Currently we are using the following approach when announcing balances Balance = value * PONT.

Example:

pub const MinimumDeposit: Balance = 100 * PONT;

Would be nice to replace this calls with function, e.g.:

CurrencyId::PONT.to_units(1.5)
CurrencyId::KSM.to_units(100.0)

After refactoring it should looks so:

pub const MinimumDeposit: Balance = CurrencyId::PONT.to_units(100.0);

Requirenments:

• [ ] Function should return Balance (u64)
• [ ] We should care about Balance in u64 if we overflow it, we should return u64
• [ ] We should care about units smaller than minimal in e.g we provide 1.0008 for currency with 3 decimals, we should have 1000 as u64 return)
• [ ] All places where we used old-fashion variant should be converted