SES-2039: now use GET method for remote SPARQL endpoints when the URL would be less than 8192 characters
SES-2040: re-introduced .setAdditionalHttpHeaders method
Merge commit 'f04e96140337ca8ea3f4f12db89b66dc9bb9e975' into 2.8.x
SES-2040: as requested, now return a read-only view of the additional headers, and also check for null before setting the headers on the SparqlSession object
minor whitespace fix
SES-2040: avoid NPE if no HTTP headers are set and their value is requested
SES-2040: comment formatting
SES-2039: encode full query before checking it length
SES-2040 : Cleanup style, switch to Collections.emptyMap to avoid nulls

Null checks may be useful in some cases to check if there are any
settings, but it isn't a big deal in the general case case so we still
support nulls in the setters for backwards compatibility, but map them
to Collections.emptyMap internally.
Add more developers to contributor list in README.md
Merge branch 'SES-2039' into 2.8.x