This is a long overdue cleanup around the ideas of entering
numbers in Flowee Pay.
The core dataclass BitcoinValue now keeps track where the number
came from, either user input or some calculation. This allows
us to have the Fiat and the Coin price stay in sync without weird
problems.
The one we type uses a string, the price field that we are not typing in
is then a slave and we follow the auto-generated number as the
source.
This solves a host of known issues:
* Editing of value objects is much more consistnnt and predictable now.
* Switching to a different fiat type now properly re-calculates the
values that are slaved. So if the primary is a BCH value then the fiat
value gets the new exhange rate instantly applied.
* Switching to a different fiat type properly applies having a separator
So if you go from euro to Japanese yen, we now remove the separator
and the numbers behind it.
* Changing the app setting from BCH to mBCH now properly updates all
amounts. Notice that the user-typed string wins, if you typed 2 and
then change to mBCH we assume you wanted 2, not 2000.
* Paste now works more logcally.
* Cursor is no longer sometimes invisible, requiring backspace to make
it show up.
And last we now protect against too large numbers. It is seen as an
error to type a number above 21 million BCH.
Fixes#19
This new allows a value to be set as a number, for instance from the
user reading a QR code, and the "typed-value" is created from this
in order to allow the user to edit it instead of overwrite it.
tomFlowee