Allow the New PyDev Project wizards to permit project creation in empty workspace folders.

Small change: instead of prohibiting non-default project locations that overlap with the
workspace, make only the workspace folder itself prohibited. Allow projects to be created
in workspace folders that lack a .project file, regardless of whether the "Default Location"
box is checked.
Allow (un)marking PyDev folders as source folders with the PyDev right-click context menu.

When right-clicking on a folder/project in the Package Explorer, allow the "PyDev" section
of the context menu to set the selection as a source folder (or to a non-source folder).
Make XML processing in InterpreterInfo independent of default encoding.
interpreterInfo.py emits now pure ASCII with XML-character-references.
It is now possible to use a Python interpreter located in a non pure
ASCII path.
Fix an invalid UTF-8 error while running Python unit tests.
For Python2, if a Python-file has a path that contains non ASCII
characters and the file system encoding is not UTF-8,
pydev_runfiles_xml_rpc.py created an invalid XMLRPC request.
This commit sets the encoding of the XMLRPC request to the file system
encoding.
During Python debugging the debugger sends file names as part of the
thread suspend message. If the debugger is running on Python2 file names
are byte strings encoded in the file system encoding. This patch
converts the names to UTF-8. Without this patch, the debugger GUI is
unable to locate the python source files.
Allow faster file-finding when searching for resource declarations in linked files.

Ctrl+clicking on file resources to find their declarations now performs much faster on
linked files, as doing so no longer prompts the user to select the correct file to open out
of a list of all possible locations for the declaration (which occurs if multiple instances
of the linked file are in the workspace). Instead, the declaration-containing file opened is
the one within the same project as the file currently being worked on.
Providing code-completion for docstrings in sphinx format.
Providing coloring for markups in docstrings.
FastStringBuffer now implements CharSequence.
Enable faster file-finding when debugging linked files.

When debugging linked files, Eclipse now searches for a the file in the current project that
matches the link target rather than asking the user to choose the correct file out of a list
of applicable ones (which happens if multiple files link to the same target).
When searching a project for a file to open, search through all referenced projects as well.

In PySourceLocator, searching for a file to open with createEditorInput now not only searches
the project passed to it for the desired file, but all of the referenced projects too.
Console hyperlinks that link to errors now link to files in the launched project.

Rather than opening an arbitrary appplicable file, hyperlinks that appear in the console
when an error occurs now attempt to open a file in the most-recently launched project
when clicked.
In New PyDev Project wizard, fix project creation bug & use recursive search for Python files.

Make the following improvements to the New PyDev Project wizard (specifically, its first page):

1. Fix a bug where it was possible to create a new project in a workspace folder with the
"use default" setting chosen in the project creation wizard, even if that folder contained
a .project file.

2. When searching for existing Python files in the project location, now recursively search
existing folders in the location for Python files too.
Added utility to split on whitespaces.
Merge pull request #48 from AndrewFerr/exsources

Allow the New PyDev Project wizards to permit project creation in empty ...
Using PythonPathHelper to check if a file is a valid .py or __init__ file (made some fixes when checking if it's a valid __init__ file).
Merge pull request #49 from AndrewFerr/aferrazz_dev

Prevent duplicate path names in a project's PYTHONPATH when creating src...
Not doing copy of Set.
Merge branch 'addons' of https://github.com/AndrewFerr/Pydev into AndrewFerr-addons
Merged functionality to add/remove source folder with context menu. Did changes to add icon and check if pythonPathNature is not null.