Remove antiquated LMS envs files

These all date back to 2012 and are hard-coded for specific course runs.

lms/envs/devgroups/courses.py

-
-# We intentionally define lots of variables that aren't used, and
-# want to import all variables from base settings files
-# pylint: disable=wildcard-import, unused-wildcard-import
-
-from ..dev import *
-
-CLASSES_TO_DBS = {
-    'BerkeleyX/CS169.1x/2012_Fall': "cs169.db",
-    'BerkeleyX/CS188.1x/2012_Fall': "cs188_1.db",
-    'HarvardX/CS50x/2012': "cs50.db",
-    'HarvardX/PH207x/2012_Fall': "ph207.db",
-    'MITx/3.091x/2012_Fall': "3091.db",
-    'MITx/6.002x/2012_Fall': "6002.db",
-    'MITx/6.00x/2012_Fall': "600.db",
-}
-
-
-CACHES = {
-    'default': {
-        'BACKEND': 'django.core.cache.backends.memcached.MemcachedCache',
-        'LOCATION': '127.0.0.1:11211',
-        'KEY_FUNCTION': 'util.memcache.safe_key',
-    },
-    'general': {
-        'BACKEND': 'django.core.cache.backends.memcached.MemcachedCache',
-        'LOCATION': '127.0.0.1:11211',
-        'KEY_PREFIX': 'general',
-        'VERSION': 5,
-        'KEY_FUNCTION': 'util.memcache.safe_key',
-    }
-}
-
-SESSION_ENGINE = 'django.contrib.sessions.backends.cache'
-
-
-def path_for_db(db_name):
-    return ENV_ROOT / "db" / db_name
-
-
-def course_db_for(course_id):
-    db_name = CLASSES_TO_DBS[course_id]
-    return {
-        'default': {
-            'ENGINE': 'django.db.backends.sqlite3',
-            'NAME': path_for_db(db_name)
-        }
-    }

lms/envs/devgroups/h_cs50.py

-
-# We intentionally define lots of variables that aren't used, and
-# want to import all variables from base settings files
-# pylint: disable=wildcard-import, unused-wildcard-import
-
-from .courses import *
-
-DATABASES = course_db_for('HarvardX/CS50x/2012')

lms/envs/devgroups/m_6002.py

-
-# We intentionally define lots of variables that aren't used, and
-# want to import all variables from base settings files
-# pylint: disable=wildcard-import, unused-wildcard-import
-
-from .courses import *
-
-DATABASES = course_db_for('MITx/6.002x/2012_Fall')

lms/envs/devgroups/portal.py

-"""
-Note that for this to work at all, you must have memcached running (or you won't
-get shared sessions)
-"""
-
-# We intentionally define lots of variables that aren't used, and
-# want to import all variables from base settings files
-# pylint: disable=wildcard-import, unused-wildcard-import
-
-from lms.envs.devgroups.courses import *
-
-# Move this to a shared file later:
-for class_id, db_name in CLASSES_TO_DBS.items():
-    DATABASES[class_id] = {
-        'ENGINE': 'django.db.backends.sqlite3',
-        'NAME': path_for_db(db_name)
-    }