Change web_vulns.confidence from text to string

[#49937603]

Mdm::WebVuln#confidence's column was a text even though code was
treating it as an integer.  It was not a problem before because
Mdm::WebVulns were not being validated after being reloaded and
confidence was cast to text.
Merge branch 'master' into bug/web-vulns-confidence-type

Conflicts:
	lib/metasploit_data_models/version.rb
Validate Mdm::WebVuln#params

[#49617323]

Add ParametersValidator that checks that Mdm::WebVuln#params has type
signature Array<Array(String, String)> and that the parameter name is
not blank.
JRuby compatible calling convention

[#49617323]

JRuby does not allow self.<method> for protected methods, so remove the
self. and just make the methods private since there is no longer a local
variable and method name collision as in the original validator code.
Merge pull request #23 from rapid7/bug/mdm-web-vuln-params-export

[Delivers #49937603]
[Delivers #50019049]