Multi sourceset amps

[vierbergenlars]

1. Refactor the Amp task type to be more flexible:
   • Make config and web a CopySpec instead of a File pointing to the root directory to copy. This fixes Support configuring Amp task file properties with CopySpec #8
   • Make licenses, libs and deLibs a ConfigurableFileCollection so items can easily be added and removed from the collection without having to manipulate the list directly.
2. Deprecate ampConfig configuration block, move configurations to sourceSets. Example
   • sourceSets is used by the java plugin to create multiple, (partially or fully) independent source trees. These are usually packaged in separate jars as well. Now, let's add an amp configuration to each sourceset that takes the jar that is created and puts it inside an amp. As with source sets as used by the java plugin, configurations and tasks are fully independent and prefixed with the sourceset name when it is not the main sourceset. The eu.xenit.amp plugin configures an amp for the main sourceset by default.
   • When no module.properties file exists, automatically generate a module.properties file based on the project configuration.
   • Configure a module.properties or file-mapping.properties file directly from your build.gradle
3. Drop support for gradle < 4.10, so we can start using gradle properties and providers and lazy configuration of tasks.

All old properties on Amp and ampConfig are still available and configure the new properties and configuration when they are used. Linking for ampConfig is provided by and isolated in a LegacyAmpPlugin that can be disabled later.
Using deprecated properties or configuration logs a warning. A stacktrace to the usage of a deprecated function is added to the warning when running gradle with --info.