fixed: error when no project's .ico file

Absence of this file is not an error. Just no MAINICON resource.
improve and fix: test icon file existence during execution but not initialization

Also, fix error when icon is a long path with spaces in it.
fixed: error when .dproj file is from older Delphi version than used one

In simple case can compile Delphi 2007 project with Delphi 2010, but
.dproj file sturcture is different. So, error occured while getting
version info. But it's just an absence of version info that should not
cause an error.
fixed: Delphi tasks do not call actions

Actually, they do not call super `execute` method.
fixed: redundant files in a packaged gem

Binaries are created after tests run. They are included into a packaged
gem. Avoid this.
gemspec: set `rake` version
improve: allow to redefine dcu output directory
fixed: alias for Forms is Vcl.Forms in Delphi XE
improve: make able to force compile console application
improve: Dcc32Task: populate .platform method

To allow redefine it "outside".
refactoring: rename @dcc32Tool to @dccTool (before adding Android platform support)
refactoring: move out Rake::Delphi::Dcc32Tool class to the separate module
refactoring: introduce Dcc32Task.recreate_dcc_tool method
improve: add String.starts_with? method
improve: use <project>.dpr without full path

As far as some dcc compiler's do not "understand" full path.
Also, dcc is run in .dpr's folder.
improve: introduce `dcc_options` option

Also, DccTool.options.
refactoring: envvariables.rb: public/private sections
improve: dcc32Tool: trace messages
fixed: envvariables: var is not expanded if set in different case
improve: name libs task after appropriate owner task