conda/artiq-dev: fix channel list

Now, with conda 4.1 packages are sorted by channel, version, build
number in decreasing priority. The highest matching package is
taken. https://conda.io/docs/user-guide/tasks/manage-channels.html

For the artiq-dev environment, the m-labs/label/dev channel should be
first, then the main channel, then defaults, and then conda-forge
(community supported packages).

closes #864

conda/artiq-dev.yaml

@@ -2,9 +2,9 @@
 # $ conda env create -f conda/artiq-dev.yaml
 name: artiq-dev
 channels:
-  - defaults
-  - conda-forge/label/main
   - m-labs/label/dev
   - m-labs/label/main
+  - defaults
+  - conda-forge/label/main
 dependencies:
   - artiq-dev

conda/artiq-doc.yaml

@@ -2,10 +2,10 @@
 # $ conda env create -f conda/artiq-doc.yaml
 name: artiq-doc
 channels:
-  - defaults
-  - conda-forge/label/main
   - m-labs/label/dev
   - m-labs/label/main
+  - defaults
+  - conda-forge/label/main
 dependencies:
   - python>=3.5.3,<3.6
   - sphinx=1.4.8

doc/manual/installing.rst

@@ -37,18 +37,18 @@ Installing the ARTIQ packages
 
 First add the conda-forge repository containing ARTIQ dependencies to your conda configuration::
 
-    $ conda config --add channels http://conda.anaconda.org/conda-forge/label/main
+    $ conda config --prepend channels http://conda.anaconda.org/conda-forge/label/main
 
 Then add the M-Labs ``main`` Anaconda package repository containing stable releases and release candidates::
 
-    $ conda config --add channels http://conda.anaconda.org/m-labs/label/main
+    $ conda config --prepend channels http://conda.anaconda.org/m-labs/label/main
 
 .. note::
     To use the development versions of ARTIQ, also add the ``dev`` label (http://conda.anaconda.org/m-labs/label/dev).
     Development versions are built for every change and contain more features, but are not as well-tested and are more likely to contain more bugs or inconsistencies than the releases in the ``main`` label.
 
 Then prepare to create a new conda environment with the ARTIQ package and the matching binaries for your hardware:
-choose a suitable name for the environment, for example ``artiq-main`` if you intend to track the main label or ``artiq-2016-04-01`` if you consider the environment a snapshot of ARTIQ on 2016-04-01.
+choose a suitable name for the environment, for example ``artiq-main`` if you intend to track the main label, ``artiq-3`` for the 3.x release series, or ``artiq-2016-04-01`` if you consider the environment a snapshot of ARTIQ on 2016-04-01.
 Choose the package containing the binaries for your hardware:
 
     * ``artiq-kc705-nist_clock`` for the KC705 board with the NIST "clock" FMC backplane and AD9914 DDS chips.