Gui enhancements

[claudio4j]

Hi, I wrote some small enhancements accordingly to https://issues.jboss.org/browse/HAL-265

The contributions are:

• case insensitive filter and filter for text in the middle for: environment properties and deployed applications
• test datasource connection for domain mode (it is in runtime -> datasource)
• flush connection for domain mode (it is in runtime -> datasource)
• added help text to ctrl+click assign deployment to multiple groups

[rhusar]

Might want to squash the commits together and add Jira number to the commit message... ;-)

[heiko-braun]

Thanks for the contribution Claudio. I did squash the commits and merged it manually.