Rename "container" to "image"

- Updated `wwctl upgrade` to handle updates
- Maintained `.Container` and `.ContainerName` in tstruct
- Added `ContainerName()` methods to node and profile objects
- Added `--container`, `-C` aliases to wwctl commands (`<node|profile> <add|set>`)
- Added `wwctl container` alias
- Added support for `container_exit.sh` if `image_exit.sh` is not found

Signed-off-by: Jonathon Anderson <janderson@ciq.com>

internal/pkg/config/mounts.go

@@ -1,13 +1,13 @@
 package config
 
-// A MountEntry represents a bind mount that is applied to a container
+// A MountEntry represents a bind mount that is applied to an image
 // during exec and shell.
 type MountEntry struct {
 	Source    string `yaml:"source"`
 	Dest      string `yaml:"dest,omitempty"`
 	ReadOnlyP *bool  `yaml:"readonly,omitempty"`
 	Options   string `yaml:"options,omitempty"` // ignored at the moment
-	CopyP     *bool  `yaml:"copy,omitempty"`    // temporarily copy the file into the container
+	CopyP     *bool  `yaml:"copy,omitempty"`    // temporarily copy the file into the image
 }
 
 func (this MountEntry) ReadOnly() bool {