more connections refactoring, add more tests

...cle/truffle/r/nodes/builtin/base/ConnectionFunctions.java

...runtime/src/com/oracle/truffle/r/runtime/RConnection.java

...le.r.runtime/src/com/oracle/truffle/r/runtime/RError.java

...est/src/com/oracle/truffle/r/test/ExpectedTestOutput.test

...ruffle.r.test/src/com/oracle/truffle/r/test/TestBase.java

...le.r.test/src/com/oracle/truffle/r/test/all/AllTests.java

...t/src/com/oracle/truffle/r/test/failing/FailingTests.java

...m/oracle/truffle/r/test/library/base/TestConnections.java

...rc/com/oracle/truffle/r/test/rpackages/TestRPackages.java