Add Wait/Retry to handle transient errors

We frequently run into issues where Chocolatey receives a 503 or other transient error when installing or upgrading a package. We use Chocolatey via scripts that have dependencies on packages being installed, if an upstream package fails, the entire build fails.

It would be nice to have a configurable number of retries and a wait period between retries.

Also, An escalating wait period would also be a nice feature

Example: 3 Retries / 5 seconds

``` bash
00:00 - choco install -y googlechrome
-- Error 503 (1st error)
[wait 5s]
00:05 - choco install -y googlechrome (1st retry)
-- Error 503 (2nd error)
[wait 10s]
00:15 - choco install -y googlechrome (2nd retry)
-- Error 504 (3rd error)
[wait 15s]
00:30 - choco install -y googlechrome (3nd retry)
```