Support snap aliases

[anonymouse64]

Using snap aliases with snap run is currently not supported, observe:

$ snap install test-snapd-glxgears 
$ snap run test-snapd-glxgears
error: cannot find app "test-snapd-glxgears" in "test-snapd-glxgears"
$ snap alias test-snapd-glxgears.glxgears test-snapd-glxgears
error: cannot perform the following tasks:
- Setup manual alias "test-snapd-glxgears" => "glxgears" for snap "test-snapd-glxgears" (cannot enable alias "test-snapd-glxgears" for "test-snapd-glxgears", it conflicts with the command namespace of installed snap "test-snapd-glxgears")
$ snap alias test-snapd-glxgears.glxgears glxgears
Added:
  - test-snapd-glxgears.glxgears as glxgears
$ snap run glxgears
error: cannot find current revision for snap glxgears: readlink /snap/glxgears/current: no such file or directory

The only way to currently do this is to specify the /snap/bin/ program and omit --use-snap-run.