first line of string template does not indent injected lines.

[jurgenvinju]

Describe the bug

rascal>aaa = "a\nb\nc";
str: "a\nb\nc"
rascal>"  <aaa>"
str: "  a\nb\nc"
rascal>
cancelled
rascal>"
>>>>>>>'   <aaa>"
str: "\n   a\n   b\n   c"

• the interpolation on the second line works fine, it adds the two spaces in front of every line
• the interpolation on the first line does nothing
• of course the first line is different from the second line, because we parse the whitespace after the ' to know exactly which whitespace to use, while in the first line after the " anything goes.
• fixing this requires some design decisions

[jurgenvinju]

This is the workaround:

rascal>"
>>>>>>>'  <aaa>"[1..]
str: "  a\n  b\n  c"