Small improvements on the mining page UX

- INDEXING_BLOCKS_AMOUNT = 0 disable indexing, INDEXING_BLOCKS_AMOUNT = -1 indexes everything
- Show only available timespan in the mining page according to available datas
- Change default INDEXING_BLOCKS_AMOUNT to 1100

Don't use unfiltered mysql user input

Enable http cache header for mining pools (1 min)

frontend/src/app/interfaces/node-api.interface.ts

@@ -68,6 +68,7 @@ export interface SinglePoolStats {
 export interface PoolsStats {
   blockCount: number;
   lastEstimatedHashrate: number;
+  oldestIndexedBlockTimestamp: number;
   pools: SinglePoolStats[];
 }