Make use of VCS base class.

Fixes:
- Cannot diff a file that does not belong to a project
- Cannot commit when a temporary diff/log view is open
  due to the current file pointing to a temporary directory
- git's project-related actions not passing the correct
  relative path.

Implementation:
- Centralize code to listen for Qt Creator's relevant state changes
  in VCSBasePlugin, dispatching the changes to the instances affected.
  (avoiding multiple invocations of searches/QFileInfo on current).
- Do the same for the corelistener catching closing SubmitEditors.
- Introduce VCSBasePluginState representing the relevant state
  (current file/project).
- Call git with working directory set and relative arguments
- Remove setEnabled/isEnabled() logic of IVersionControl
- Pass toplevel from VCSManager to avoid duplicate searches.

 * Remove unnecessary headers.
 * Remove hardly used variables.
 * QTC_ASSERT before using a pointer which might be 0.

Reviewed-by: dt

For example std::string, which is a typedef of std::basic_string.

Reviewed-by: Thorbjørn Lindeijer <thorbjorn.lindeijer@nokia.com>

Several special cases that are handled by the CPPEditor did not take
into account code that was using tab characters.

Task-number: QTCREATORBUG-292
Reviewed-by: Roberto Raggi

 * This makes sure this widget gets the same margins as all the
   others.

Reviewed-by: dt

 We are targetting nothing below netbooks. These devices have screens
 that usually are 1024px wide (or wider), so this increase should be OK
 there.

 The 100px bonus do help a bit when editing environment variables, etc.

Reviewed-by: dt

Reviewed-by: dt

 * Init is really setting up the UI, so rename it to setupUi.

Reviewed-by: dt

 * Fix graphical glitches when rendering the detailsbutton.
 * Add copyright headers while touching this file.

Reviewed-by: dt

 * Add expanded signal.
 * Add copyright headers.
 * Improve setExpanded method as well as setting a widget.

Reviewed-by: dt

Reviewed-by: kh1

Otherwise we need to parse the cbp file, which happens only if the
buildconfiguration gets active. Also try to decouple a few internals a
little bit by using signals. The CMakeProject still handles a few things
directly instead of via signals, more to come eventually.

Should fix a lot of corner cases, might introduce a few bugs.
Also rename functions/slots to be better named.

Generic Project Manager and CMake Project Manager are missing from this
patch.