Further Bug Fixes and Improvements to 2.0

+ Convert _rez_query_yaml and _rez_query_package_yaml scripts to new style 'rez query' commands.  This command is required by the Doxygen cmake macro.  Arguably this functionality would be better merged into `rez info` however the distinct difference is this is working with an unreleased package where as `rez info` appears more suited to the lookup of released packages.
+ Allow ${....} to go unformatted in a string.  Particularly useful for old-style commands that are being converted to Rex, but also means new-style commands of the form `env.BAR = '{root}/blah/${FOO}'` should be valid.
+ Set the default VCS tag name back to {version}.  Accidentally committed {name}-{version}.
+ If the old-style export command is already surrounded by quotes, remove them.  They will be added back by the interpreter.
+ When getting a Version object from a VCS tag, use the new regex provided in the settings.  This is required if the VCS tag name has been changed so we can always match the version part which we need to make a Version object.