ALLJOYN-1852: Fixed ttl message unmarshal bug. Refactored sessionlessObj message expiration

Change-Id: I51c4f8bee906f38efa245d67539916b7d70b98a2
ALLJOYN-1249: Place files associated with C++ in a dist/cpp folder

Separating the C++ files into there own folder makes the SDK distribution simpler to understand for developers.

Place files associated with winRT in a dist/winRT folder

Fixed doxygen dependency issues

In some situations the code would try and install the documents
before they were generated. This fixes the dependency making sure
the documents were generated before scons tries to install the
API documentation.

Google Test for alljoyn_c needs its own test scripts for buildbot.

ALLJOYN-1425 - Improve top-level README files (DRAFT WORK-IN-PROGRESS)

Change-Id: Ieca14d7e5e07c2da49b219e96dedd4474b7e802b