Update README.md

Added two modifications to make the descriptions more clear.
Merge pull request #4557

92b8587 Update README.md (elkingtowa)
Harmonize importprivkey and importaddress documentation
qt: Use fixed-point arithmetic in amount spinbox

Fixes various issues and cleans up code

- Fixes issue #4500: Amount widget +/- has floating point rounding artifacts
- Amount box can now be emptied again, without clearing to 0

Also aligns the amount to the right, as in other places.
qt: Remove unused functions from BitcoinUnits

Remove two functions that are now unused.
Fixes after code reviews
remove unnecessary includes (squashme)
change default unit to BTC not 0 (squashme)
fixes (squashme)
ui: Make sure sendcoinsentry signals only connected once

Move signal connections to constructor where possible.