Inject button in issue filter input box to save customized filter

[eschao]

In issue filter input box, a icon button is injected here to save user customized filter.

The below functions will be implemented:

• Inject a save button in issue filter input box
• Save filter for repository respectively
• Edit/remove saved filter
• Show customized filters in Filters dropdown list

[eschao]

Available in v0.4.0 now