+ Add check for reference to environment variable that should be replaced with rex.
+ Fix unused imports, typo, and missing imports.
+ Remove incorrect use of os.pathsep.
+ Extend regex.
+ Update build method on build system to usw BuildType enum.
+ Set CMake variable REZ_BUILD_TYPE based on value of BuildType enum.
+ Set CENTRAL CMake variable if in backwards compatibility mode and BuildType is central.
+ Set REZ_IN_REZ_RELEASE environment variable if in backwards compatibility mode and BuildType is central.
+ Update Doxygen macro to use new REZ_BUILD_TYPE CMake variable.
+ Prefer py files over yaml and txt when loading certain resources.
adding missing arg in call to _add_build_actions
+ Fix bugs in the help command.
-almost fixed graph generation, cycles still to do
-finished rewrite of solver graph generation, should fix bug related to PR #120
+ Add support for package version and system variables to the namespace expansion.
-added graph prune configurable option
Merge remote-tracking branch 'mark/convert_old_commands_fix' into 2.0

Conflicts:
	src/rez/_sys/_setup.py
	src/rez/build_process.py
	src/rez/package_resources.py
	src/rez/packages.py
	src/rez/resolved_context.py
	src/rez/solver.py
	src/rez/status.py
	src/rez/tests/test_rex.py
	src/rez/vendor/version/version.py
	src/rezplugins/release_vcs/stub.py
Merge remote-tracking branch 'mark/backwards_compatibility_for_central_variable' into 2.0

Conflicts:
	src/rez/build_process.py
	src/rezplugins/build_system/bez.py
Merge remote-tracking branch 'mark/prefer_py_files' into 2.0

Conflicts:
	src/rez/package_resources.py
Merge remote-tracking branch 'mark/help_command_bug_fix' into 2.0
-fixed bug where 'default_shell' config entry was being ignored. This in turn
meant the shell-specific tests were only using bash.
-fixed shell-specific bugs found once above bug fixed.
-note that PR #121 addressed this problem elsewhere; this fix supercedes however.
-added support for literal and expandable strings in rex
-shell plugins now provide string expansion methods
-fixed remaining bugs wrt rex literal strings and quote escaping
-added unit test in test_shells
-upped internal context serialise version from 3.1 -> 3.2, reflecting the change in the resolve graph