Add APIs to host simple GLSL sandbox shaders

- Add APIs to get elapsed and delta time.
- Add a protected function to read an asset file as a String to MajVjActivity.
- Remove MajVjProgram methods that accept InputStream.
Add glsl sandbox  compat vertex shader to assets

- Fix a bug that readAssetAsString() does not contain LF.
Add glsl sandbox  compat vertex shader to assets

- Fix a bug that readAssetAsString() does not contain LF.