Add total estimated hours and total spent hours for the issue to ViewCustomize.context.

[onozaty]

I need an easy way to get total spent time and total estimated time to achieve the following.

• Show popup when spent-time exceeds estimated-hours field for issue redmine-view-customize-scripts#132

These information are displayed on the screen, but are difficult to retrieve because they are not on the form. The display format changes depending on the language.