DodoApp: Support volume requests

Users can define volumes section under app, and for each volume
corresponding env variable will be passed down to the application.

Change-Id: I8da9d5e1ca652cdb2f0196fcba1b6242064d057f
diff --git a/apps/app-runner/main.go b/apps/app-runner/main.go
index ca99831..10d74ae 100644
--- a/apps/app-runner/main.go
+++ b/apps/app-runner/main.go
@@ -25,6 +25,7 @@
 type Command struct {
 	Bin  string   `json:"bin"`
 	Args []string `json:"args"`
+	Env  []string `json:"env"`
 }
 
 func CloneRepository(addr string, signer ssh.Signer, path string) error {
diff --git a/apps/app-runner/server.go b/apps/app-runner/server.go
index 665f493..865f724 100644
--- a/apps/app-runner/server.go
+++ b/apps/app-runner/server.go
@@ -98,6 +98,7 @@
 			Dir:    *appDir,
 			Path:   c.Bin,
 			Args:   args,
+			Env:    c.Env,
 			Stdout: os.Stdout,
 			Stderr: os.Stderr,
 		}