lazy initialization of highlight pens and brushes for DebugVariableViewer

Constructors wx.Pen() and wx.Brush() require wx.App to exist already.
That causes crash during import of the control,
because import is done before calling main application code.

.project

.directory

syntax: regexp
^tests/.*/build$
^.idea/.*
syntax: regexp
^.*\.pyc$
syntax: regexp
^.*~$
syntax: regexp
^.*\.swp$

bug_report.*\.txt
i18n/.*.new$
revision

doc/_build
doc/locale