Attempt to shut down any PC that just threw.

Alleviates the symptoms of error sin the class of #1002016.
Reinstating the JDT reconcile override in ScalaSourceFile.

It's still called by the JDT Indexer. Fixes #1002016.
This is a partial revert of ee2f5a7. See also [this comment](https://github.com/dragos/scala-ide/commit/ee2f5a7606647b0380fad1820d74b29ff01a096c#commitcomment-4675824).
Merge pull request #622 from huitseeker/issue/1002016

Reinstate call to JDT reconciler for side-effects
prevent NPE on classpath problems

I hope this fixes the NPE I'm seeing on the Scala compiler project
when I forget to set the SCALA_BASEDIR variable in linked resources.
(It also needs to be set in the "classpath variables" settings panel,
but when you forget that one you get a nice error in the error log.)

```
java.lang.NullPointerException
at scala.tools.eclipse.ClasspathManagement26357anonfun.apply(ClasspathManagement.scala:405)
at scala.tools.eclipse.ClasspathManagement26357anonfun.apply(ClasspathManagement.scala:404)
at scala.collection.immutable.List.foreach(List.scala:302)
at scala.tools.eclipse.ClasspathManagement.validateBinaryVersionsOnClasspath(ClasspathManagement.scala:404)
at scala.tools.eclipse.ClasspathManagement.checkClasspath(ClasspathManagement.scala:299)
at scala.tools.eclipse.ClasspathManagement.isClasspathValid(ClasspathManagement.scala:199)
at scala.tools.eclipse.ScalaProject.isClasspathValid(ScalaProject.scala:93)
at scala.tools.eclipse.ScalaBuilder.build(ScalaBuilder.scala:59)
at org.eclipse.core.internal.events.BuildManager.run(BuildManager.java:733)
```
Merge pull request #635 from adriaanm/npe

prevent NPE on classpath problems
Allow task tags to start with a special sign

The implementation of `CombinedWordRule` has changed insofar that a word
that is already read but not matched can now be rescanned by other
rules. Previously the word was associated with a default token.

Fixes #1000991
Refactorings in wizard components
Merge pull request #630 from sschaef/t-wizards-refactoring

Refactorings in wizard components
Merge pull request #633 from sschaef/t1000991-task-tags-with-special-start-sign

Allow task tags to start with a special sign