Share an Augeas handler for all resources of a provider
Use a new Augeas handler for @aug_version to avoid messing up with the shared handler when resource is not defined
Fix provider specs
kernel_parameter: fix grub2 provider for shared handler
sysctl: fix provider for shared handler
sysctl and pg_hba: make tmpdir outside of contexts
shellvar: Fix @logs test in specs (value= succeeds, flush fails)
sshd_config: reuse aug handler in match_exists?
Call super in providers that redefine flush
Add a new supported? method to replace using_post_resource_eval? and regexpi_supported?
Improve errors when loading and saving files

  shellvar: save error message doesn't include target anymore
shellvar: fix unset with Augeas 1.2.0
shellvar: simplify unset management code
Use Augeas 1.2.0 as reference version for tests again