TAC Import check of arguments in the translated message is a bit too strict

At the moment it seems that the check on placeholders is too restrictive, as it seems that it demands that for a given argument you use it the same number of times in the original message.

For example:

Say the original message defines an argument

{1}
and it uses it as

original.message=Something {0} else {1}

refer to

{1}

TAC demands that your translation uses {1}

two times.

It should be enough to validate that no unexisting arguments are used in the translated message and that each argument defined in the original message is used at least one time.