Fix failing unit test (conversion of strings via factors)

I was a bit surprised by this, because the bug must have been around for a while
(we need to add continuous integration for R provider and run the tests automatically!)

The problem is that the IntegerVector in recent versions of R.NET only
succeeds when the value is *not* a factor (there is an explicit check
`not (sexp.IsFactor())`) and so the pattern was never matched in the
convertor. This change uses R.NET only to check that the value is *some*
vector and then explicitly checks for numeric vectors (without ruling out
factors).
Merge pull request #89 from tpetricek/factor.fix2

Fix failing unit test (conversion of strings via factors)
Register InteropServer as a well-known singleton

Issue #86 is caused by the server object being gc'd at the server. This
can be prevented by registering the server object as a
WellKnownServiceTypeEntry and specifying that the service be provided as
a singleton. This guarantees that the lifetime of the server object will
be the lifetime of the server process.
Merge pull request #90 from dcharbon/feature/prevent-disconnection

Register InteropServer as a well-known singleton
Adopt latest R.Net for concurrency fixes

The latest R.Net 1.5.12 and RDotNet.FSharp 0.1.5 include concurrency
fixes that resolve issue #64. They might also resolve RInteropServer
disconnection issues that have been seen, though this will take some
further testing to verify.
Incorporate feedback from @tpetricek

Removed locking from RInteropServer. Removed all references to
C_StackSize since the RDotNet default is what is needed. Fixed
RWrapperGenerator.fsproj so that it doesn't use elements not supported
on Mono. Remove unnecessary reference to DesignTime assembly in Tests.
Improve exception forwarding for RInteropServer

When an exception is thrown during the execution of a method in
RInteropServer that exception cannot be returned to the client unless it
is serializable. All methods now wrap their behavior in a try statement
that catches all exceptions and grabs the message from non-serializable
exceptions to re-raise as a serializable exception.
Merge branch 'feature/new-RDotNet' of https://github.com/dcharbon/FSharpRProvider into rdotnet_1.5.11