[Halld-offline] hdpm update

[Nathan Sparks]

I have made a number of updates to hdpm over the past week.
https://github.com/JeffersonLab/hdpm/wiki

1. Added rcdb, gluex_root_analysis, and gluex_workshops as packages.
gluex_workshops is not included in the main templates (master, home-dev, and jlab-dev).
There is a special build template called workshop-2016 for building the software that was used in this year's workshop.
This is intended for use outside of JLab, and is configured to build all the dependencies.
---
Remember that the physics workshop software is already installed on the JLab CUE. 
To use it, first set your HALLD_MY environment variable and then:
source /group/halld/Software/workshops/env_ws.csh

2. Added support for Ubuntu 16.04.
There is a linking error when building gluex_root_analysis that I do not understand yet, but the other package builds seem okay.
Note that Linux Mint 18 is also supported, since it is binary compatible.

IMPORTANT
3. Changed the default pkgs (packages) directory structure to <pkg>/<version> from <pkg>-<version>.
This helps to keep the pkgs directory better organized when you have installed multiple versions of a package.
It is recommended to change to the new default directory structure on your next update of hdpm.
Of course, there is no rush ... update when you are ready; Follow these steps to migrate:
1. Change to hdpm directory.
2. git pull
3. source setup.[c]sh
4. julia src/migrate.jl
This script will migrate your directories of the form <pkg>-<version> to <pkg>/<version> in your “pkgs” directory.
5. hdpm select <template_id> (to update your settings)
If you have saved custom settings (to the templates directory), you need to update them manually.

4. The name of the environment setup script now corresponds to the name/id of the template used to create it. For example,
jlab-dev.csh, workshop-2016.sh, master.sh, etc.. instead of hdenv.csh. This prevents you from overwriting your previous
environment script when you generate a new one based on a different template.

Please let me know if you have any questions.

-Nathan