Adding --skip-sha256 option to catalog management

Allows one to assume download or cached file's integrity is correct.
Can save a lot of time if checksum of those file as already been checked.
Useful with --package-cache
7 jobs from skip-sha256-option in 1 minute and 38 seconds (queued for 1 second)
latest
Status Job ID Name Coverage
  Test
passed #156036
Code Coverage

00:01:38

passed #156037
Code Quality

00:00:21

passed #156038
Data Migration

00:01:13

passed #156039
Missing Migrations

00:00:22

passed #156035
Tests: C locale

00:01:25

passed #156033
Tests: Jessie/Python-3.4

00:01:27

passed #156034
Tests: Stretch/Python-3.5

00:01:22