Implement convenient ToString() methods for nodes and locations

[KvanTTT]

Or use DebuggerDisplay attribute instead. It makes the debug process more clear.

Also, I suggest using the following output line-column based format for Location:

• [l,c) - if start position equals to the end position.
• [l,c1..c2) - if start line equals to the end line, but columns are different.
• [l1..l2,c) - if start line differs from the end, but columns are the same.
• [l1,c1..l2,c2) - common format.

And the following for index-based (Roslyn-like):

• [i) - if start position equals to the end position.
• [i1..i2) - includes the first position but excludes the latest one.

[sebastienros]

I am fine with that. Do you want to create a PR for this?

[KvanTTT]

Yes, I want, but later.

[KvanTTT]

What is the reason for using array ranges int[] Range instead of typed ranges like TextSpan Range where TextSpan consist of Start and Length or Start and Stop fields? I think it's more convenient.