Release LibertyBans to Maven Central under org.libertybans namespace + deprecate space.arim packge

[A248]

Aim to release version 1.2.0 on Maven Central, under org.libertybans as the group ID and package namspace.

Firstly, this will put the API on Maven Central, which is a goal unto itself. It makes the dependency easier to access and increases trust with developers. Not only the LibertyBans API, but also its dependents (Omnibus) should ride the greater vehicle to Maven Central. Artifacts:

• org.libertybans.omnibus - former Omnibus packages
• org.libertybans.api - API packages
• org.libertybans.core & etc. - other packages, not published to Maven Central

Package namespacing
Related to the group ID, I should develop the class namespacing to move to the new package. This transition will be one step in the path to change the project namespace (#361). It fits in nicely with the Maven Central transition.

Transition plan for API consumers:

• Version 1.2.0 can deprecate the old package (space.arim.libertybans), so that existing API users can transition at their comfort. Later, if we want, we can use static initializers to detect and warn about uses of the old API.
• The new package org.libertybans.api will co-exist in version 1.2.0. Usage of the old package will redirect to it..
• Version 2.0 can just remove the old namespace. Quite simple.

In the long term, org.libertybans will hopefully do very well.