Supporting allure extensions (https://github.com/allure-framework/allure...

...-core/issues/414)

https://github.com/allure-framework/allure-core/issues/414
Allure report builder can be configured with extensions (extensions can contain additional SPI implementations, e.g. DataProvider).
Extensions string should be <dependency>[;<dependency>]* where <dependency> is string in aether format (<groupId>:<artifactId>[:<extension>[:<classifier>]]:<version>}).

Later allure maven plugin can be made configurable, as well as Jenkins plugin. For CLI we could configure allure-report-builder via system property or additional argument.