Add time-amplitude Pulses.

Allows Id(q) to return a pulse with a zero-length shape.
Add setup instructions to README.
Got DigitalAttenuator working again.

Not sure why it was so broken but it works with the ino file in the Qlab
repository now.

--CAR
Demand at least one file to plot

--CAR
Adds support for exporting to Tek5000.

Note: only tested up to producing a file. Have not yet checked that file output
looks good.

--BRJ
Add Apache license.

--BRJ
Basic reader for .awg files.

--BRJ
Add enabled to top-level instrument class.
Used new row_changed event for instrument lists.
Added tool-tips to source view.
Docstrings improvement.
Put coherence measurments together and rename T1 -> InversionRecovery
Soon to be changed ChannelGUI improvements.
Fix unequal analog/marker channel lengths.

--BRJ
Switch to PySide

--CAR
Finally working all the way through to the spectrometer.
Merge branch 'develop' into feature/enaml-GUIs

Big merge.  Probably botched something....
Conflicts:
	QGL/Channels.py
	QGL/Compiler.py
	instruments/Instrument.py
	instruments/InstrumentManager.py
	instruments/InstrumentManagerView.enaml
	instruments/MicrowaveSources.py
	instruments/MicrowaveSourcesView.enaml
Added analysers section for nework and spectrum analysers.
Add reference source to Labbrick class and condtionally display in GUI.