Complex and double numbers can be converted to String via static methods in Complex/DoubleVectorPrinter

CoercionStep split into CoercionStep and AttributableCoercionStep so that the CoercionStep can use RType and is compatible with filters.

Few builtins cast pipelines needed to be fixed or rewritten to new API

There are simple classes that represent steps in the cast pipeline,
those can be converted to nodes or any other useful representation
by provided visitors.

This means that e.g. int will go directly to the builtin and not through the cast
pipeline in the following example: arg("x").mustBe(numericValue()).asIntegerVector().findFirst().

Initial structure of intermediate representation of cast pipeline and its conversion to CastNodes.

A fix-up of the warning conditions in BypassNode

The contains method added to TypeExpr

empty vector mappers added

The first half of the cast pipelines fixed to bypass RNull and RMissing

a fix-up in CastBuilder.getCasts() method

The second half of the cast pipelines affected by the new RNull and RMissing handling fixed.

FindFirstNode invoked directly from the BypassNode; all pipelines wrapped by the BypassNode

rebased on master

The bypassReady step removed

Formatting issues fixed in RBuiltinDiagnostics

Style issues fixed in BypassNode

Adjusting the code to compile with Truffle @ 0.16 as well as the new one which doesn't throw IOException from eval-like methods