Umbrella: Modernize and modularize the build

[ebruchez]

For sanity and future-proofing, we need to take steps to break dependencies and modularize the build.

Subprojects:

• Move build to sbt, phase 1 Move build to sbt, phase 1 #2232
• Move build to sbt, phase 2 Move build to sbt, phase 2 #2805
• Automatically produce CSS from LESS Automatically produce CSS from LESS #351

Potential modules:

• misc utilities
• XML utilities
• resource manager
• XPL pipeline engine
• XML processors
• legacy XML processors (see Consider removing obsolete JAR files from distribution #1613)
• dom implementation (see Migrate to a minimal version of dom4j #2165)
• legacy XUpdate processor (see Don't use dom4j XPath APIs #2164)
• XForms engine
• Form Runner
• Form Builder

The new build system would probably use sbt.

Useful tools:

• http://www.jetbrains.com/idea/features/dependency_analysis.html
• https://github.com/sbt/sbt-web
• http://www.webjars.org/

[ebruchez]

For reference, the Scala project itself just got an experimental sbt build.

[ebruchez]

Recently created formBuilder and formRunner modules, see f28d8d8 and c71b98a and some of the subsequent commits.

[ebruchez]

Recently:

• moved XBL components to the formRunner project
• created xforms module

[ebruchez]

Moved xforms module work to #3292.