[TEP15] Implement TEP15 (support slices in fragments)
Implement TEP15 (support referencing slices in model fragments).
Added unit tests. To see it in action, you can run
from taurus.qt.qtgui.application import TaurusApplication
from taurus.qt.qtgui.display import TaurusLabel
if __name__ == '__main__':
import sys
app = TaurusApplication()
w = TaurusLabel()
model = 'sys/tg_test/1/float_spectrum#rvalue[10:5:-2]'
w.setModel(model)
m = w.getModelObj()
m.write(range(0,2560,10))
print m.getFragmentObj('rvalue[10:5:-2]')
w.resize(333,33)
w.show()
sys.exit(app.exec_())
Fixes #751 (closed)