introduce HTML tidy checks for HTML descriptions

[ivangalkin]

• create check_rules.sh and extend cppcheck_createrules.py

for each rule.xml in cxx-sensors/main/resources:
    check rule.xml with xmllint
    parse rule.xml
        for each rule in rule.xml:
            dump rule.attr("description") to tmp.ruledump
            check tmp.ruledump with tiny-html5

• fix issues w.r.t. HTML formatting and escaping
• many important HTML issues were fixed, but also many [escaping] issues which SonarQube seems to tolerate

@guwirth is there a chance to activate check_rules.sh in continuous integration? FYI it uses [linux] tools (xmllint and tidy-html5), which probably have to installed additionally.

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This change is 

[guwirth]

is there a chance to activate check_rules.sh in continuous integration? FYI it uses [linux] tools (xmllint and tidy-html5), which probably have to installed additionally.

@ivangalkin we are using Travis for testing with Linux. The entry point is the file https://github.com/SonarOpenCommunity/sonar-cxx/blob/master/.travis.yml. You can try to add your script in the script: section. In https://travis-ci.org/SonarOpenCommunity/sonar-cxx you see the LOG files.

Not sure if xmllint and tidy-html5 is pre-installed (think not). In this case you have to install it in one of the before_script, install or before_script steps.

[guwirth]

script is using a local path from your PC

[ivangalkin]

@guwirth thank you for the comments and the information about travis
since the change is already pretty large I would limit its scope to the XML adjustment
I will address the CI integration in the future pull request

[guwirth]

@Bertk ready to merge?

[guwirth]

@Bertk any comments. Will merge it this evening...