tempo: cache intermediate files

This allows much faster debug cycles on the later portions of the
algorithm
apps: bextract: make double-to-int conversions explicit
tempo: svm agreement between C++ and python

Also remove round() from C++ because MSVC doesn't have it.
bump version to 0.5.0-alpha

According to agreement with George, next version is 0.5.0.
Fixed bug where RtAudio.h was getting included even if AUDIOIO was turned off
Merge branch 'master' of github.com:marsyas/marsyas
Added more features for nextract to output.  Added ability for nextract to output features in Sonic Visualiser format, but still default to libsvm format.
Finally found that bug in RMS, it would coredump if given an input with more than one observation...
PeUtilities.cpp was including AudioSink even if AUDIOIO was off
bextract should work even if AUDIOIO is disabled.
New version of nextract with more features
cmake: move SVM(Linear)Classifier.cpp files into "marsystems" folder
cmake: enlist core source/header files in CMakeLists.txt

Reasons:

1. This is better than listing files in another file, because it allows
"make" to automatically call "cmake" when a file is added to, removed from,
or renamed in the list.

2. I don't imagine anyone contributing to Marsyas core who wouldn't know
how to enter their file at the right place in CMakeLists.txt.
synchronize branch topic/realtime with master