Adjust the oLTC Pledge Ratio

The aim of this proposal is to reduce the oLTC Tunnel Pledge Ratio(PR) to an appropriate level to increase tunnel capacity.

As you may be aware, the oLTC tunnel has reached its capacity for a while due to the price movement of LTC and the increased need for oLTC.

Currently, oBTC tunnel has been running on a PR of 105% since [BIP-11] for almost 3 months safely. On the other hand, PR for oLTC and oDOGE are still 200%.

I think it is time to lower the PR for oLTC (because oDOGE has plenty of capacity so the need is not urgent for it) to introduce more oLTC into circulation.

I have done some calculations(assume that 'Satellite City' and 'Wild Wild West' assets will not be pledged against oLTC incidents), and propose several options for the community and the dev team to consider. I hope we can reach a balance between capacity and system security.

Options: Option A: We do not change the Pledge ratio, no more oLTC will be minted.

Option B: Decreasing pledge ratio from 200% to 150%. This is a quick fix of the current problem and will introduce about 4000 more oLTC's capacity. While having the most safety buffer, we might need to do another fix very soon.

Option C: Decreasing pledge ratio from 200% to 135%. This will introduce about 12000 oLTC capacity. I think it is more than enough for couple of months based on previous demands.

Option D: Decreasing pledge ratio from 200% to 120%. This is the most aggressive option and will introduce about 34000 oLTC capacity. We have to really have faith in the BoringDao system to chose this one, and we don't need to adjust PR for a long time.