Correctly identify the Scala library on the class path, and pass it on to the Sbt builder.

* The Sbt builder uses the same mechanism as the presentation compiler to identify the
Scala library (or the JDK)
* Any scala library can be used now, including a dependent project (that defines scala.Predef).

Fixed #1000987
Fixed #1000729
Fixed #1001027

Review by @skyluc, @hubertp
Removed unused code, per @hubertp's comments.
Option for Organize Imports to keep groups written by the user.

Organize Imports now has a third option to deal with multiple
imports from a type/package which keeps the groups written by
the user instead of always expanding/collapsing them.

Fixes #1000846.
Merge pull request #113 from misto/issue/organize-keep-braces-1000846

Option for Organize Imports to keep groups written by the user.
Merge pull request #112 from dragos/issue/separate-runtime-compiletime-lib-1000729

Correctly identify the Scala library on the class path, and pass it on t...
Major refactoring of the maven build.

No bash script needed anymore. Everything is managed through maven.
The new pom at in root folder contains version information and general configuration.
org.scala-ide.build-toolchain is the root of the toolchain part
org.scala-ide.sbt.build is the root of the sdt part
The version numbers of some plugins has been upgraded

The downloaded libs have been moved to the target/lib folders, to simplify the clean up process.

The first time, run './build-all.sh (or './build-all.sh install -P scala-2.10.x' for 2.10) from the root to generate an initial build and install the top pom locally. Then use maven from any project or subproject.

Use the scala-2.10.x profile ('-P scala-2.10.x') to compile the 2.10 version.

Re #1001056
Disable the TestScalaIndenter test.

It causes other tests to fail
Updated the readme with new build instructions
Removes the tycho test workaround

The previous version of tycho (0.12.0) was using the scala-compiler jar as a osgi bundle when running the test, which was creating problems when trying to find the scala-compiler jar, which we expected inside itself ...
In 0.14.1, this behaviour cannot be reproduce, so the workaround is removed.
Clean up and simplification of the poms

Made the dependencies of library, compiler and sbt optional, so they don't have to be excluded later.
Moved the 'allowConflictingDependencies' option to the projects which require it (feature and site).
It is needed because of the mix of versions for the elements coming from the m2 repo.
Removed the dependency to aspectjrt (not needed)
Cleaned-up an invalid property definition in sbt.full.library.
Created properties for all plugin version numbers
Fixed typo
Fixed git location
Added parameter to the p2 repositories ids
Added extra compiler jar

Correctly configure optional dependencies
Adds generation of the toolchain update site

In a new maven project/folder
Merge pull request #114 from skyluc/issue/maven-refactoring-1001056

Refactoring of the build process to use only maven
Temporary disable ClasspathTest#sourceFolderLibrary test. Need to be re-enabled after pull request 115 is merged
Temporary disable ClasspathTest#binaryClassFolderLibrary too
Explicit argument to `Array.empty` for 2.10 compatibility.
Correctly copy the scala-reflect.jar for 2.10, in addition to the usual jars.
Bumped the Sbt version to the new 2.10-binary compatible version.
added .cache (generated by sbt builder) to project .gitignore
updated miglayout and log4j jar-path in core .classpath