Make casting work

[svenallers]

Hi,
I realized during some implementation that a cast you make is actually not applied. I fixed that by overriding visitCasting() in SqlFormatter. During the implementation of visitCasting() , I also realized that

if (expr.removeBrackets) {
    visit(expr)
} else {
    write("(")
    visit(expr)
    removeLastBlank()
    write(") ")
}

was a very common pattern used all over the place. I took the chance and refactored it into a single method writeExpression() to reduce the redundancy. I hope that's fine. Otherwise, I would revert it.

[svenallers]

resolves #146

[vincentlauvlwj]

Thanks for your contribution, the code is perfect, but we have to ensure the cast syntax works for all supported dialects, could you please add unit tests for each of them?

[vincentlauvlwj]

Use the writeKeyword function

[svenallers]

Done

[svenallers]

@vincentlauvlwj I added tests for each dialect. Was not as easy as I expected, because every dialect has its own restrictions as to what cast is allowed and MySql, Oracle as well as SQL Server do not allow casts from int to text...

[vincentlauvlwj]

Merged, will release in next version.