Update of codebase to conform the rules of Scalastyle

This commit contains:

- Correction of tests that rely on trailing white spaces.
- A fix of a package name in a test unit.
- Removal of trailing white spaces and tabs in the whole project.
  The changes are all done automatically with the following
  commands:

  (Conversion of tabs to white spaces)
  find . -iname "*.scala" -print0 | xargs -0 sed -i 's/\t/  /g'

  (Removal of trailing white spaces)
  find . -iname "*.scala" -print0 | xargs -0 sed -i 's/ *$//'

- To is some content added to an empty Scala file to solve a
  Scalastyle warning.
Add Scalastyle plugin

For the beginning the only rules that are activated are rules that
check for the existence of trailing whitespaces and tabs.

To run the plugin manually simply type in:

  mvn scalastyle:check

This commits contains:

- A Scalastyle configuration file in `sdt.core`. It should be moved
  to the roor directory of Scala IDE once the Scalastyle Eclipse
  plugin is fixed (at the moment it can't read configuration files
  from non Eclipse projects).
- The main POM file is updated with all necessary information to
  run Scalastyle during the build.
- For all including projects, the POM files are updated to run
  Scalastyle during the build.
- The Scalastyle nature and the configuration file for the Scalastyle
  Eclipse plugin is added for each project.
Merge pull request #416 from sschaef/introduce-scalastyle

Introduce scalastyle
Implemented `skipAllBreakpoints` for the Scala Debugger

The Scala debugger now reacts consistently to `skipAllBreakpoints` requests,
which can be triggered by users from the Debugger UI.

The enabled state of a breakpoint does now depend not just on the breakpoint
state, but also on the `BreakpointManager` state, which can be queried to know
if breakpoints should be ignored during a running debug session.  When a user
hit the `skipAllBreakpoint` button in the UI, the `BreakpointManager`'s
isEnabled state  is set to false, entailing that any enabled breakpoint should
be ignored.

Prior to this commit, we used to store in the breakpoint's marker a flag to
know if the `eventRequests` associated to the breakpoint were (or will, if
lazily loaded) enabled. However, using the breakpoint's marker for keeping
track of this information isn't safe, because markers can be shared across
multiple debug sessions. Now, this information is stored in the
`BreakpointSupport` actor.

Unfortunately, the above change made testing more difficult, as we need a way
to inspect the the `BreakpointSupport`'s requests state. At the moment, the
simplest solution was to add a new message `GetBreakpointRequestState` which
can be used to retrieve this information in tests.

Fix #1001437