Further improved parts of the code

...ava/de/kuschku/quasseldroid_ng/ExampleInstrumentedTest.kt

app/src/main/AndroidManifest.xml

...java/de/kuschku/quasseldroid_ng/service/QuasselService.kt

...ava/de/kuschku/quasseldroid_ng/ui/ServiceBoundActivity.kt

app/src/main/res/drawable/ic_add.xml

app/src/main/res/drawable/ic_arrow_right.xml

app/src/main/res/drawable/ic_check.xml

app/src/main/res/drawable/ic_debug.xml

app/src/main/res/drawable/ic_delete.xml

app/src/main/res/drawable/ic_filter.xml

app/src/main/res/drawable/ic_format_bold.xml

app/src/main/res/drawable/ic_format_fill.xml

app/src/main/res/drawable/ic_format_italic.xml

app/src/main/res/drawable/ic_format_paint.xml

app/src/main/res/drawable/ic_format_underline.xml

app/src/main/res/drawable/ic_help.xml

app/src/main/res/drawable/ic_history.xml

app/src/main/res/drawable/ic_lock.xml

app/src/main/res/drawable/ic_lock_open.xml

app/src/main/res/drawable/ic_modify.xml