feat(bitmap): add bitmap features

[bal7hazar]

Pull Request type

Please check the type of change your PR introduces:

• Bugfix
• Feature
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no API changes)
• Build-related changes
• Documentation content changes
• Other (please describe):

What is the current behavior?

No bitmap management

Issue Number: #295

What is the new behavior?

• bitmap::get_bit_at
• bitmap::set_bit_at
• bitmap::most_significant_bit
• bitmap::least_significant_bit
• bitmap::nearest_left_significant_bit
• bitmap::nearest_right_significant_bit
• bitmap::nearest_significant_bit

Does this introduce a breaking change?

• Yes
• No

fast_power has been renamed to fast_power_mod and a new fast_power derived from the previous one (without the mod operation) has been introduced.

Other information

fast_power has been made generic, revert from while to loop pattern to save gas (~10% for large power) and also to prevent overflow (an extra mul operation was done even if the remaining power was 0 due to while pattern).