add ability to reset matches but keep regions

[vyacheslavs]

after [reset] command i need always remove regions by [dregion] command again and again.
this patch adds option to [reset] command to keep current region list

[sriemer]

The idea is good. But the code style is bad once again.
If you look at handlers.h, then you should notice that options added to commands always use the underscore '_' to split words. Examples: 'scan_data_type', 'region_scan_level',... So 'reset keep-regions' makes that inconsistent. It should be 'reset keep_regions' instead.

All other options of that kind are implemented as parameters of the 'option' command. It should be discussed if something like 'option reset_keeps_regions 1' would be better to set this. Maybe @coolwanglu has a preference.

[coolwanglu]

How about

reset [all]
reset matches
reset regions

[sriemer]

Resetting regions without the matches might cause unpredicted behaviour. I would leave that out for now. The rest sounds very good.

[12345ieee]

I agree that in the current state this isn't merge-able, but the idea of chaining a dregion <correct list> to any reset is reasonable.

I'm removing it from milestones, until interest picks up for this feature and it can be implemented better.