Add documentation around catalogers, UI elements, and the event bus (#143)

* add basic documentation for catalogers (with refactoring for simplification)

Signed-off-by: Alex Goodman <alex.goodman@anchore.com>

* add docs for catalog parsers, UI, and event bus

Signed-off-by: Alex Goodman <alex.goodman@anchore.com>

* update bus phrasing

Signed-off-by: Alex Goodman <alex.goodman@anchore.com>

internal/version/build.go

@@ -7,22 +7,25 @@ import (
 
 const valueNotProvided = "[not provided]"
 
+// all variables here are provided as build-time arguments, with clear default values
 var version = valueNotProvided
 var gitCommit = valueNotProvided
 var gitTreeState = valueNotProvided
 var buildDate = valueNotProvided
 var platform = fmt.Sprintf("%s/%s", runtime.GOOS, runtime.GOARCH)
 
+// Version defines the application version details (generally from build information)
 type Version struct {
-	Version      string
-	GitCommit    string
-	GitTreeState string
-	BuildDate    string
-	GoVersion    string
-	Compiler     string
-	Platform     string
+	Version      string // application semantic version
+	GitCommit    string // git SHA at build-time
+	GitTreeState string // indication of git tree (either "clean" or "dirty") at build-time
+	BuildDate    string // date of the build
+	GoVersion    string // go runtime version at build-time
+	Compiler     string // compiler used at build-time
+	Platform     string // GOOS and GOARCH at build-time
 }
 
+// FromBuild provides all version details
 func FromBuild() Version {
 	return Version{
 		Version:      version,