* replace hard-coded strings with existing constants
* proxy port
* * custom proxy port and hostname inputs
* typesafety, refactor, linting, unit tests
* relocate ProxyConfiguration in app structure
* remove unused editTextPreference fn
* allow preference category to have no title
* refactor proxy prefs hierarchy/dependency
* convert EmojiPreference and EmojiCompatFont to Kotlin
* move preference related to to dedicated preference package
* update proguard-rules.pro
* reformat & add comment
* maintain disposable information in EmojiPreference instead of EmojiCompatFont