add template output (#1051)

* add template output

Signed-off-by: Jonas Xavier <jonasx@anchore.com>

* remove dead code

Signed-off-by: Jonas Xavier <jonasx@anchore.com>

* fix template cli flag

Signed-off-by: Jonas Xavier <jonasx@anchore.com>

* implement template's own format type

Signed-off-by: Jonas Xavier <jonasx@anchore.com>

* simpler code

Signed-off-by: Jonas Xavier <jonasx@anchore.com>

* fix readme link to Go template

Signed-off-by: Jonas Xavier <jonasx@anchore.com>

* feedback changes

Signed-off-by: Jonas Xavier <jonasx@anchore.com>

* simpler func signature patter

Signed-off-by: Jonas Xavier <jonasx@anchore.com>

* nit

Signed-off-by: Jonas Xavier <jonasx@anchore.com>

* fix linter error

Signed-off-by: Jonas Xavier <jonasx@anchore.com>

internal/config/application.go

@@ -38,6 +38,7 @@ type Application struct {
 	// -q, indicates to not show any status output to stderr (ETUI or logging UI)
 	Quiet              bool               `yaml:"quiet" json:"quiet" mapstructure:"quiet"`
 	Outputs            []string           `yaml:"output" json:"output" mapstructure:"output"`                                           // -o, the format to use for output
+	OutputTemplatePath string             `yaml:"output-template-path" json:"output-template-path" mapstructure:"output-template-path"` // -t template file to use for output
 	File               string             `yaml:"file" json:"file" mapstructure:"file"`                                                 // --file, the file to write report output to
 	CheckForAppUpdate  bool               `yaml:"check-for-app-update" json:"check-for-app-update" mapstructure:"check-for-app-update"` // whether to check for an application update on start up or not
 	Anchore            anchore            `yaml:"anchore" json:"anchore" mapstructure:"anchore"`                                        // options for interacting with Anchore Engine/Enterprise