Better handling of multi-line comments for all generators

[wing328]

• to cover all remaining generators
• to handle block comment starter (e.g. /*, =begin)
• to add underscore instead of removing the block comment starter and terminator

[wing328]

For #3201

[edstover]

Hi,

I think this change has the side-effect of changing media type declarations from "*/*" to "*_/_*". I've noticed this in generated API specifications when the following yaml is used:

consumes:
- application/json
- text/plain
- "*/*"
produces:
- application/json

The resulting Java API when generated using "spring" for the language looks like this:

produces = { "application/json" },
consumes = { "application/json", "text/plain", "*_/_*" },
method = RequestMethod.GET)

Can the substitution with underscores be suppressed for media types?

[wing328]

@edstover "/" is better handled via #4155

Please pull the latest master to give it a try.