Allow more special characters in version label

One change in this release. A lot of special character errors were happening because a lot of characters are illegal in S3 filenames but are legal in the version label itself in Elastic Beanstalk. So now we replace any characters other than letters, numbers and - and _ with a dash, - in the S3 filename, but leave the version label as it is.

The only character that Elastic Beanstalk itself has a problem with in a version label is the forward slash /, so you still can't use that one.