Limit number of simultaneous file extractions to prevent hardlock

Added helper extraction functions
chmod & chown is now set after a folder's extraction to prevent permission issues

internal/threadmanager/manager.go

@@ -0,0 +1,23 @@
+package threadmanager
+
+type Manager struct {
+	c chan int
+}
+
+func NewManager(maxRoutines int) *Manager {
+	m := &Manager{
+		c: make(chan int, maxRoutines),
+	}
+	for i := 0; i < maxRoutines; i++ {
+		m.c <- i
+	}
+	return m
+}
+
+func (m *Manager) Lock() int {
+	return <-m.c
+}
+
+func (m *Manager) Unlock(n int) {
+	m.c <- n
+}