Drop support for SQALE xml file

[duncanp-sonar]

Support for SQALE has been deprecated for several versions of SonarQube, and it is now possible to specify supported debt information in the rules.xml file instead.

In addition, the components used to import SQALE now rely on the guava, which adds several megabytes to the size of the template plugin.

Required changes

• drop the command line support for specifying a SQALE file to import
• drop the generation and insertion of the SQALE file
• enable the users to edit the rules.xml file instead (check: ?most of this work done in a separate branch already?)