UI/UX - New component for difficult adjustment. (#602)

* Add next difficulty blocks.
Add next difficulty target date.
Add next difficulty total progress.
Add ajustment difficulty avg min per block.

* Fix typo.

* Trigger difficulty calculation every 5 seconds.

* Add rxjs timer to difficultyEpoch.

* Fix pipe.

* Fix small bar position.

* Change i18n strings.

* Fix typo.

* Add time-until component.

* Speed up difficultyEpoch timer to 1000 ms.

* Fix values to 2 decimal places.

* Add title to fee and difficulty adjustment cards.

* Add title outside the card.

* Fix title to center position.

* Add other titles.

* Add new transalations strings.
Refactor time span component.

* Fix difficulty adjustment i18n string.
Fix duplicated i18n strings.

frontend/src/app/shared/shared.module.ts

@@ -11,6 +11,7 @@ import { ScriptpubkeyTypePipe } from './pipes/scriptpubkey-type-pipe/scriptpubke
 import { BytesPipe } from './pipes/bytes-pipe/bytes.pipe';
 import { WuBytesPipe } from './pipes/bytes-pipe/wubytes.pipe';
 import { TimeSinceComponent } from '../components/time-since/time-since.component';
+import { TimeUntilComponent } from '../components/time-until/time-until.component';
 import { ClipboardComponent } from '../components/clipboard/clipboard.component';
 import { QrcodeComponent } from '../components/qrcode/qrcode.component';
 import { FiatComponent } from '../fiat/fiat.component';
@@ -25,6 +26,7 @@ import { ColoredPriceDirective } from './directives/colored-price.directive';
   declarations: [
     ClipboardComponent,
     TimeSinceComponent,
+    TimeUntilComponent,
     QrcodeComponent,
     FiatComponent,
     TxFeaturesComponent,
@@ -65,6 +67,7 @@ import { ColoredPriceDirective } from './directives/colored-price.directive';
     NgbPaginationModule,
     NgbDropdownModule,
     TimeSinceComponent,
+    TimeUntilComponent,
     ClipboardComponent,
     QrcodeComponent,
     FiatComponent,