[BUG] Enable TableInterpreter to trim leading and trailing whitespace

[TungstnBallon]

Adds two properties to TableInterpreter: skipLeadingWhitespace and skipTrailingWhitespace. Both are true by default.
If enabled InternalRepresentationParserVisitor will trim whitespace for integer, decimal and boolean.

Part of #641.

[georg-schwarz]

LGTM.

Having it in the TableInterpreter seems a good solution to me.

We might want to define it column-specific in the future, esp. if we have a nicer syntax to apply transformations. Example (just spitballing):

    block TestBlock oftype TableInterpreter {
		header: false;
		columns: [
			"index" oftype integer <- stripWhitespaces,
			"name" oftype text,
			"flag" oftype boolean <- stripWhitespaces
		];\
	}

[joluj]

I agree with @georg-schwarz's comments.

We might want to define it column-specific in the future

I agree, but it's something for another PR.