[FIX-issue#99] Allowing negative logic index values

[RPG-coder-intc]

Issue #99

• Now one can use negative values in indices for indexing or subset slicing.
• This effect is applied on BusSubset that is used by Logic slice()
• Indirectly this effect is also passed to function that uses slice() like operator[] (indexing operator) and getRange()

[RPG-coder-intc]

• getRange() Exception handling are redundant as it is handled by BusSubset() contructor within slice()

[RPG-coder-intc]

Just needs unit testing and documentation! Great start!

Thanks Max!! Will do it asap.

[RPG-coder-intc]

Just needs unit testing and documentation! Great start!

Made Changes as requested!

[mkorbel1]

PR #174 is adding a bunch more lint checks, which will probably flag some new issues for you if you get in after that (when you pull the changes in). I'll wait a little bit to give you an opportunity to beat the PR in, but in the next day or two it will go in and then you'll have a little clean-up to do.

[RPG-coder-intc]

Thanks!