Reorganize packages, closes #79

- All packages go into either cmd or pkg directories
- Most packages renamed
- Server packages moved into pkg/server
- sanitize moved into webui, as that's the only place it's used
- filestore moved into pkg/storage/file
- Makefile updated, and PKG variable use fixed

pkg/storage/lock.go

@@ -0,0 +1,19 @@
+package datastore
+
+import (
+	"strconv"
+	"sync"
+)
+
+type HashLock [4096]sync.RWMutex
+
+func (h *HashLock) Get(hash string) *sync.RWMutex {
+	if len(hash) < 3 {
+		return nil
+	}
+	i, err := strconv.ParseInt(hash[0:3], 16, 0)
+	if err != nil {
+		return nil
+	}
+	return &h[i]
+}