Improving issues format in Redmine

[pegrau]

Motivation

The information the plugin currently sends to Redmine in order to create issues could be improved, in both format and rules descriptions.

Changes

All changes in this PR are related to the creation of the Redmine Issue:

• The subject will only have the name of the Sonar Rule.
• The issue body will contain the description of the Rule, previously transformed to Textile format (instead of the original format: HTML).

The followings tags are supported:

<p>, <a>, <code>, <ul>, <li>, <pre>, <h1>, <h2>, <h3>.

Any other tag will be ignored, but the design allows to easily add new HTML tags processors.