[input][input-amount] Relationship with currency

[erikkroes]

The currency of an input-amount is added as an "after". There is no programmatic relationship between the input and the "after", while there is visually. Either a builtin solution or an instruction like "add visually hidden information to the label" should be added.

For example, the label could read: Amount (in euros). With the part in parenthesis visually hidden.

[tlouisse]

This was fixed by 0d687bb#diff-89d83a2b790350b38f42f92fce0e9ff7