Add Functions!AntiFunction as a simple variant of Inverse.

Note, AntiFunction comes with a Java module override and is, thus,
significantly faster.

[Feature]

Explicitly convert CSV!CSVWrite parameter to TupleValue to handle case

where parameter is a FcnRcdValue.

[Feature]

A non-existent file is defined to have zero CSV records.

Easily write headers if file doesn't exist:

```tla
ASSUME CSVRecords("output.csv") = 0 => CSVWrite("Headers...", <<>>,
'output.csv")
```

[Refactor][TLC]

A non-existent file is defined to have zero CSV records.

Easily write headers if file doesn't exist:

```tla
ASSUME CSVRecords("output.csv") = 0 => CSVWrite("Headers...", <<>>,
'output.csv")
```

[Refactor][TLC]

Add 'SymDiff' operator for the symmetric difference of two sets

Addresses tlaplus#46

Add 'SymDiff' operator for the symmetric difference of two sets

IOUtils!atoi

[Feature]

IOUtils!atoi

[Feature]

Synchronize Json!serialize operators in case multiple workers

write to the same trace file concurrently.

tlaplus#47

[Bug]

NullPointerException in Json module when domain of FcnRcdValue is

represented symbolically as an IntervalValue.

Fixes Github issue "Bad format of Json trace printing"
tlaplus#47

[Bug]