Review formatting of boolean strings (in ToString() methods and similar)

[paulirwin]

Context: See PR #914

Any ideas what the string returned here is supposed to represent?

Java: spanNear([f:lucene, f:net, f:solr], 0, true)
.NET: SpanNear([f:lucene, f:net, f:solr], 0, True)

This looks like something that may be copied and pasted somewhere to me, but it may just be a textual description. If the former, we should probably at least strive to match the case of the boolean. I am guessing the name is the correct casing for .NET, though.

Of course, we are probably using upper case for all booleans converted to string in .NET, because that is what .NET does by default. So, whatever the fix, it should be applied consistently in all queries.

Originally posted by @NightOwl888 in #914 (comment)