Bug: problems with persistence

When saving `while`, `for`, `repeat`, or maybe other statements, some problems occur. For example, we have the following algorithm:
```
ALGORITHM A1 IN ST:
VAR_TEMP
Index : INT;
Sum: INT;
END_VAR
Index := 0;
Sum := 0;
WHILE Index < 10 DO
Sum := Sum + Index;
Index := Index + 1;
END_WHILE;
END_ALGORITHM
```

After reopening MPS, it shows the algorithm in a changed way:
```
ALGORITHM A1 IN ST:
VAR_TEMP
Index : INT;
Sum : INT;
END_VAR
Index := 0;
Sum := 0;
WHILE Index < 10 DO
no statements
END_WHILE;
Sum := Sum + Index;
Index := Index + 2;
END_ALGORITHM
```

And when trying to parse this algorithm in code: `org.fbme.lib.iec61499.parser.STConverter.parseStatementList`, the `org.antlr.v4.runtime.InputMismatchException` occurs because input text is `Index := 0;
Sum := 0;
WHILE Index < 10 DO
Sum := Sum + Index;
Index := Index + 1;
END_WHILE;
` and the error is at the 49th symbol - after `WHILE Index < 10 DO`

I think the problem is in `org.fbme.lib.iec61499.stringify.PrinterBase.escapeXML`:
```
text = text.replace("\n", "
")
text = text.replace("\"", """)
text = text.replace("&", "&")
```
After "\n" is replaced by `
`, the "&" is replaced by `&`. So, "\n" is replaced by `&#10;` and it is written to a file (saved)

Returning to the text when the ANTLR exception is thrown. The parser reads the saved model with our algorithm. After that, the model is unescaped in `org.fbme.lib.iec61499.parser.BasicFBTypeConverter.AlgorithmConverter.extractDeclarationBody`:
```
val stText = stBodyElement.getAttributeValue("Text")?.unescapeXML()
```

Let's look at `unescapeXML()` block:
```
.replace("
", "\n")
.replace(""", "\"")
.replace("&", "&")
```
As you see, our `&#10;` is replaced by `
`. After that, ANTLR throws`org.antlr.v4.runtime.InputMismatchException`.

I believe that, in order to address this issue, it would be advisable to adjust the order of escaping in the following manner: `org.fbme.lib.iec61499.stringify.PrinterBase.escapeXML`
```
text = text.replace("\n", "
")
text = text.replace("\"", """)
text = text.replace("&", "&") // this line must be the first in replace commands
```

Start with org.fbme.lib.iec61499.stringify.PrinterBase.escapeXML and org.fbme.lib.iec61499.parser.BasicFBTypeConverter.AlgorithmConverter.extractDeclarationBody, then trace org.fbme.lib.iec61499.parser.STConverter.parseStatementList. Reproduce the save-and-reopen flow using the algorithm in the issue and verify that XML escaping round-trips newlines correctly and parsing no longer raises InputMismatchException.

Written by the indexing model from the issue text.