Refactoring of AnalyzerResult in order to address issue #13

Refactoring of AnalyzerResult in order to address issue #13

Add AnalyzerAttributes to handle the metadata in AnalyzerResult and store the Analyzer parameters
Attributes include :
- [x] sampleRate, blockSize, stepSize
- [ ] version of the analyzer (or Timeside release ?)
- [ ] audio source file name
- [x] analysis parameters
- [ ] precision of the results data (float, long, ...)
- [ ] stereo / mono / left / right channel management during analysis ?

AnalyzerResult now include a @property field "properties" containing a dictionnary of the following stats about the results data :
- mean
- median,
- std
- min
- max

Also change the result value return by AubioTemporal because mean and median are now include in "properties"