AudioLoader memory leak on python steaming mode

[g-roma]

Creating an instance of AudioLoader (streaming) on python allocates memory that is never collected.

Test:

from essentia.streaming import AudioLoader
f = "test/audio/recorded/musicbox.wav"
for i in range(1,1000): a= AudioLoader(filename=f)

[dbogdanov]

The problem is more generic and will affect any streaming algorithm. Algorithms with

_source.setBufferType(BufferUsage::forLargeAudioStream)

set will fail faster. Probably, the Sources are not cleaned correctly in their implementation.

[dbogdanov]

Two simplest examples to reproduce the bug:
1)

from essentia.streaming import *
for i in range(1,1000): a= AudioLoader()

from essentia.streaming import *
for j in range(1,10000):
    for i in range(1,10000):
        a= MFCC()

Affects any streaming algorithm.

[jlyda]

This issue is fixed in 2436db3