bumped default scala version 2.9.x -> 2.10.x
Correct syntax highlighting for while-keyword

While syntax highlighting correctly recognizes the while-keyword as a
keyword, semantic highlighting treats it as a method. Because semantic
highlighting is activated after its syntax counterpart, it overwrites
the previous detected colors.

The new behavior omits all occurrences of LabelDef in the AST because
they don't regularly appear in Scala sources but represent while- and
do-while-keywords internally in the compiler. Hence they must not be
highlighted.

Fix #1000984
README now contains exhaustive developers guidelines
Merge pull request #283 from dotta/feature/developer-guidelines

README now contains exhaustive developers guidelines
Merge pull request #282 from huitseeker/feat/bump-scala-default-version

Bumped default scala version 2.9.x -> 2.10.x review by @dotta
Gracefully handle unknown JDK classpath containers.

If the JDK required by the project does not exist, `getClasspathContainer` returns null.

Fixed #1001249.
Merge pull request #281 from sschaef/issue/while-highligting-correction

Correct syntax highlighting for while-keyword - Fix #1000984
No need to block the whole workspace to add a marker.

Resources do the necessary scheduling already inside `createMarker`.
Formatting.
Issue errors if the class path contains cross-compiled libraries with a different major version of the Scala compiler.

Identify jars with `name_2.x.y-??.jar` and compare the plugin version with the one in the name, issue errors for each library that is not compatible.

Fixed #1001441.
Reviewer's comments.
Merge pull request #286 from dragos/issue/classpath-binary-validation

Validate cross-compiled binaries on the classpath
wip

Conflicts:

	org.scala-ide.sdt.core/src/scala/tools/eclipse/ScalaSourceViewerConfiguration.scala
isolated ui logic
never call pos.setLength(0)