integrate RError.nyi with conditional handling; add write mode textConnection

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

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

...rc/com/oracle/truffle/r/runtime/conn/TextConnections.java

.../src/com/oracle/truffle/r/runtime/data/RStringVector.java

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

...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

...racle/truffle/r/test/library/base/TestSimpleBuiltins.java