Foundation: doxygen typo fixes
TTValue: cleanup of some old cruft and adding a few comments.
TTValue: after a number of iterations of the code, we were left with a mixture of inconsistent at() and [] operator usage.  In most cases we are already bounds-checked or bounds-safe, so there is no need for the extra overhead incurred by calling at() instead of using the [] operator.
TTValue: adding comment about the reserve() call in the empty constructor.
TTValue: can now contain error codes -- this means we can return a value from a function and still return an error code if it fails instead of forcing us to use potentially clumsy function arguments for our return values.
TTValue: some optimizations for float64 conversion
DSP: adding comments, removing the never-used calculateProcess() method.
TTDataObject: minor cleanup
TTAudioSignalArray::setSignal() implementation moved out of the header and into the c source file.  As a result the deprecation warnings therein are quarantined to the building of the DSP lib and don't pollute every single project with a dependency on DSP.
TTObject: a change to the preferred method of sending messages (the old method of sending messages still works).  Now you pass the input as an arg (as before) but the output comes back as the return value of the method.  This opens the doors for a number of interesting possibilities in terms of graph construction and direct calls that previous was clumsy (at best).
Merge
Set prefix as /usr on Linux

The macro JAMOMA_EXTENSIONS_INSTALL_PREFIX can be set in order to change
the path to the extensions.

The organization on Linux is now as follows :
- Libs : /usr/lib/libJamomaFoundation.so
- Exts : /usr/lib/jamoma/libScenario.ttso
- Includes : /usr/include/jamoma/TTFoundation.hpp
Move files from .txt to .cmake  to have coloring in IDEs