Properties file for custom mappings

[jjohannes]

Have a more DSL-like construct like map("org.apache.commons.lang3", "org.apache.commons:commons-lang3"), currently there is only moduleNameToGA.put("org.apache.commons.lang3", "org.apache.commons:commons-lang3"). New construct should have a clean way to define coordinates and (optionally) a capability, like:
map("org.apache.commons.lang3", "org.apache.commons:commons-lang3", "org.apache.commons:commons-lang3-test-fixures")

Support a custom properties file as the primary way to define additional mappings. This would then be in line with modules.properties delivered with this plugins. And mapping from that custom file can be propagated back (as ideally, the mapping are globally unique for most Modules).

Short notation for capabilities that correspond the "standard" feature variants setup should be supported. For example:
org.apache.commons.lang3=org.apache.commons:commons-lang3|test-fixures