Add strict validation to snippet file names

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
Sanitize snippet file name in raw headers

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
Fix snippet factory

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
Merge branch 'sanitize-snippet-file-name' into 'master'

Validate and sanitize snippet file name

Fixes #1816

See merge request !1322
Update CHANGELOG with snippet validation change

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>