Rapid rebalance strategy - Squeezing every sats out of a route

[ziggie1984]

This is a preliminary PR for other users to also test the new rapid rebalance strategy. Which basically does the follwing:

When a route is found it will rebalance with an increasing amount (doubling), the new thing is, that it will go down to the min amount when decreasing the amount again. Only potential downside is, that you will try more routes hence failing more routes if no liquidity is available, but from my personal experience it's definitely worth the cost.

[M1ch43lV]

I am testing the changes, and it works very well without bugs! When rapid rebalancing is in action the rebalancing amounts goes up and then down to the minimum until all liquidity of the channel is transfered to your node. For node runner an improved function! Thanks @ziggie1984! Great job.
For whom who want to try out without waiting until merged you can do following steps if you are working with separate users:

$ sudo su - regolancer
$ git clone https://github.com/rkfg/regolancer
$ cd regolancer
$ git status
$ git fetch origin pull/56/head:7ced2fa
$ git status

If you are not successful then try this

$ git checkout 56017f5 
$ git status

Compile & check version

$ go build
$ regolancer --version

Rename the old version and link the new compiled version to the correct path

$ mv /home/regolancer/go/bin/regolancer /home/regolancer/go/bin/regolancer.old
$ ln -s /home/regolancer/regolancer/regolancer /home/regolancer/go/bin/regolancer

[ziggie1984]

Ok I also tested it locally, would appreciate some feedback for the PR. Also seeing from the comments that its already used successfully in the wild.
For a routing node I found it very useful to go in this direction when rapid rebalancing.

[M1ch43lV]

Also the latest commit of ziggie1984 works without problems