Set initial value of multiple values list to default value (if available)

[barafael]

Hi :)

I noticed that currently, if a multiple_values field has a default value, this value does not appear initially in the list of arguments (which initially is empty). But when clicking the "Reset to default" button, the default value is entered as the first entry in the multiple_values sequence.

This change pre-populates the multiple_values vector with the default value, if one is given. On "Reset to default", this state is restored. The default value can also still be edited and removed with the - button.

Let me know what you think :)

[barafael]

I realize this may be suboptimal default behaviour. Converting to draft to prevent merging.