Add MaxDuration option and context/timeout, Add `time()` time in seconds, usec resolution, Add `sleep()`

[ldemailly]

• time()
• sleep()
• cleanup extension.go / added MustCreate()
• max duration enforcement
• limit stack dump to 10 eg

  16:11:05 [E] Errors: [<err: context deadline exceeded, stack below:>
  (i,n,prod)=>{if i==n+1{return 1./(prod*prod*n)}self(i+1,n,prod*(1-1./(2*i)))}
  (i,n,prod)=>{if i==n+1{return 1./(prod*prod*n)}self(i+1,n,prod*(1-1./(2*i)))}
  (i,n,prod)=>{if i==n+1{return 1./(prod*prod*n)}self(i+1,n,prod*(1-1./(2*i)))}
  (i,n,prod)=>{if i==n+1{return 1./(prod*prod*n)}self(i+1,n,prod*(1-1./(2*i)))}
  (i,n,prod)=>{if i==n+1{return 1./(prod*prod*n)}self(i+1,n,prod*(1-1./(2*i)))}
  ... 1484 more ...
  (i,n,prod)=>{if i==n+1{return 1./(prod*prod*n)}self(i+1,n,prod*(1-1./(2*i)))}
  (i,n,prod)=>{if i==n+1{return 1./(prod*prod*n)}self(i+1,n,prod*(1-1./(2*i)))}
  (i,n,prod)=>{if i==n+1{return 1./(prod*prod*n)}self(i+1,n,prod*(1-1./(2*i)))}
  (i,n,prod)=>{if i==n+1{return 1./(prod*prod*n)}self(i+1,n,prod*(1-1./(2*i)))}
  (i,n,prod)=>{if i==n+1{return 1./(prod*prod*n)}self(i+1,n,prod*(1-1./(2*i)))}]

• 34

Fixes #34 Fixes grol-io/grol-discord-bot#4