Age range check

[0xturboblitz]

• Adding age range check to circuits and app

[remicolin]

This PR adds a range check for user age, closing #41

Two inputs have been added to the main circuit:

• current_date[6]: the current date in YYMMDD format represented as an array of numbers, e.g. [2, 4, 0, 1, 0, 1].
• majority[2]: the age on which the circuit will perform the range check, represented in ASCII format, e.g. [49, 56] for 18.

The SBT has been extended with one attribute: older_than, which will have majority[2] as its value.