Allow optional include pattern

[TheE]

The fileset used when copying the translation files currently uses a hard-coded include pattern of **/**. In some cases it might be helpful, if users could overwrite this include pattern as needed.

For example, I am having a project with multiple sub-projects, each project has it's own set of translations. On crowding, the translations of all project are stored in one single project in subfolders like so:

project1/
project2/
project3/

To properly resolve the translations per-module, in every module I need to manually specify witch modules I do not want; if I could instead use an include pattern, it would be a s simple as

subprojects {
  crowdinDownload {
    //API etc.
    includePattern = project.name + '/**'
  }
}