Leave a trace of the source git hash in the help message

When dealing with test or snapshot dbuild versions, it may
be useful to know what git hash they were built from. That
bit of information is now displayed in "dbuild --help".
Some refactoring in Assemble, splitting out patchPomDependencies()
When adjusting poms and ivy.xmls, also patch the version

In order to share more easily code between the Assemble build
system and the Ivy/Aether ones, also cater for the case in
which the version number was replaced while moving the (pom/
ivy.xml) files, and adjust them in the module descriptions
as appropriate.
Move OrgNameVerFilenamesuffix where other build systems can see it
Refactor patchIvyDependencies() in AssembleBuildSystem
More modularization in Assemble
First implementation of the Aether build system
Reduce verbosity
Use ~/.m2/repository as a read-only remote maven repository
Work in progress (Aether)
More work in progress (Aether)
The Aether build system now works as intended
Adding placeholder for missing dependency checking in Aether build system
Better debug messages
Add Aether support to download sources & javadoc as well