Escape collate (#220)

[doyaaaaaken]

Hi, I try to implement fix for #220 bug.
If it's not correct, do not mind to close this PR.

[Tapac]

Thank you for a PR. It looks pretty well but maybe it worth to add protected escape() function to StringColumnType to make code more readable?

[doyaaaaaken]

@Tapac
Thank you! I fixed it in 912ddb9 .

[Tapac]

And one more improvement - extract characterMap to something like a companion object or top-level private variable to prevent map allocation for every escape invocation.

Also, escape(value.toString()).forEach { append(it) } is not very effective. It should be changed to append(escape(value.toString())) or keeped as it was before.