refactor(cache): rewrote/refactored cachedb functionality to use interface (#667)

Moved boltdb to a driver implementation for such interface
Added CreateCacheDatabaseDriver in controller
Fixed default directory creation (boltDB will only create the file, not the dir
Added coverage tests
Added example config for boltdb
Re-added caching on subpaths, rewrote CreateCacheDatabaseDriver
Fix tests
Made cacheDriver argument mandatory for NewImageStore, added more validation, added defaults
Moved cache interface to own file, removed useRelPaths from config
Got rid of cache config, refactored
Moved cache to own package and folder
Renamed + removed cache factory to backend, replaced CloudCache to RemoteCache
Moved storage constants back to storage package
moved cache interface and factory to storage package, changed remoteCache defaulting

Signed-off-by: Catalin Hofnar <catalin.hofnar@gmail.com>

pkg/api/config/config.go

@@ -22,8 +22,9 @@ var (
 
 type StorageConfig struct {
 	RootDirectory string
-	GC            bool
 	Dedupe        bool
+	RemoteCache   bool
+	GC            bool
 	Commit        bool
 	GCDelay       time.Duration
 	GCInterval    time.Duration
@@ -95,13 +96,7 @@ type LogConfig struct {
 }
 
 type GlobalStorageConfig struct {
-	Dedupe        bool
-	GC            bool
-	Commit        bool
-	GCDelay       time.Duration
-	GCInterval    time.Duration
-	RootDirectory string
-	StorageDriver map[string]interface{} `mapstructure:",omitempty"`
+	StorageConfig `mapstructure:",squash"`
 	SubPaths      map[string]StorageConfig
 }
 
@@ -143,9 +138,11 @@ func New() *Config {
 		Commit:          Commit,
 		ReleaseTag:      ReleaseTag,
 		BinaryType:      BinaryType,
-		Storage:         GlobalStorageConfig{GC: true, GCDelay: storage.DefaultGCDelay, Dedupe: true},
-		HTTP:            HTTPConfig{Address: "127.0.0.1", Port: "8080", Auth: &AuthConfig{FailDelay: 0}},
-		Log:             &LogConfig{Level: "debug"},
+		Storage: GlobalStorageConfig{
+			StorageConfig: StorageConfig{GC: true, GCDelay: storage.DefaultGCDelay, Dedupe: true},
+		},
+		HTTP: HTTPConfig{Address: "127.0.0.1", Port: "8080", Auth: &AuthConfig{FailDelay: 0}},
+		Log:  &LogConfig{Level: "debug"},
 	}
 }