Support Windows 10 1903 Light Theme

When launch from test framework, the Application.StartupPath looks like "C:\PROGRAM FILES (X86)\MICROSOFT VISUAL STUDIO\2019\COMMUNITY\COMMON7\IDE\EXTENSIONS\TESTPLATFORM" which may not have write permission.

Move GetWindows10SystemThemeSetting() to Util.cs
WindowsThemeMode use enum
Status var windowsThemeMode rename to windowsThemeMode
Used `if else` to replace `switch case`
Delete legacy commint (Some code).
Increase contrast for icon.

Removed redundant method call

- Portable mode ON: executable file's folder
- Portable mode OFF: current user's temp folder

* Translation
* Environment Variables support

#1273

* Rename variable 'traffic' to 'trafficPerSecondQueue' and 'trafficInfoQueue'

* Remove class QueueLast<T> by using linq Queue.Last()

* Slight changes, such as rename, move several variables from function domain to class domain to improve performance.
Logic remains the same.

* Update the logic of copying queue from Controller to View.

* Move the TrafficInfo declaration into LogForm class

Overwise, the VS UI designer does not work.

- change dir name to "ss_win_temp" to make things clear.
- throw any exception caught when creating temp folder

To workaround silly cleaning softwares and careless users.

Signed-off-by: Syrone Wong <wong.syrone@gmail.com>

Signed-off-by: Syrone Wong <wong.syrone@gmail.com>

This reverts commit a61b10bb67.

This reverts commit 0d4d01af3b.

This reverts commit 5ba0dffa5d.

This reverts commit f2b8e91f81.

This reverts commit b04c59d8e6.

No more http->socks5 transform.

Remove some debug output

This fix the proxy issue on win10 insider preview.

Use singleton mode for hotkey callbacks.

Signed-off-by: Syrone Wong <wong.syrone@gmail.com>

Signed-off-by: Syrone Wong <wong.syrone@gmail.com>