+ Stubbing out a change to get the build command to show a conflict graph.
+ Tidy up the implementation and rename a few things.
+ Remove this module, functionality move to rez.util and rez.env.
+ Logic moved to rez.env.
+ Reimplement the logic from rez.cli._util to retrieve the current context file.
+ Update to use relocated code.
+ Update to use relocated code.  Also improve logic to catch a non-existant current rxt (either not set or deleted).
+ Functionality to view and write a graph.
+ Change option to fail graph.
+ Update based on changes to build process.
+ Fix a problem with the import.
+ Handle the case that a graph isn't available.
Merge remote-tracking branch 'mark/build_conflict_view_graph_option' into testing_1

Conflicts:
	src/rez/build_process.py
	src/rez/cli/_util.py
	src/rez/cli/build.py
	src/rez/cli/context.py
	src/rez/tests/test_build.py
	src/rez/util.py