Sdss-tree

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- Added `phase` property to python `tree`. Tracks phase of current 'sdsswork' environment.
- Modified module setup to create "default" symlink for lua modules
- Added `write_old_paths_inifile` method to generate a version of the old sdss_paths.ini file
- Adding new paths for DR16+; VACs for EBOSS_LSS, ATLAS, SPECTRO_LENSING, BOSS_QSO

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- Removed specific version requirement 1.0.0 for sdss_access in module setup

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- Added correct path for DR9 PHOTOSWEEPS
- Corrected APOGEE_ASTRONN path in DR16
- Added BCAM_DATA_2S to DR16

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- Added prereqs to tree module files for sdss_access/1.0.0 and sdsstools/0.1.7

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- Major changes to environment configuration files
- Incompatible with 2.x versions
- Implements versioning of DR config files and `sdss_access` paths
- Each config file now inherits from another config file using `base` keyword.
- Each DR config now only contains new or modified definitions for that DR.
- New configs for internal releases can now be created, e.g. mpl9.cfg.
- Explicit case is recognized for environment names and tree ini sections
- Deprecated and Removed sdss_paths.ini file
- New PATHS ini section in environment config files defines `sdss_access` paths
- Symbol for "special function" path definition has changed from `%` to ``
- Refactored ``compute_changelog`` function to return dictionary and compute PATHS differences
- Added changelog compute functions ``compute_environment_changes``, and ``compute_path_changes``.
- Added changelog print functions ``print_environment``, and ``print_paths``.
- Moved tests out of ``tree`` python package to top level.
- Deprecated included logger and config in favor of ``sdsstools`` logger and config.
- Simplified python package setup.cfg and consolidated requirements files

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Added
^^^^^
- new function ``compute_changelog`` to print difference between two tree environments
- new sphinx documentation on all DR tree environments and environment changes between DRs

Changed
^^^^^^^
- added wave keyword to mangacube/rss paths to handle LOG/LIN switch
- updated Tree python code to handle new cfg inheritance and versioning