moved all files to src folder

src/Aggregation/AbstractAggregation.php

src/Aggregation/AvgAggregation.php

src/Aggregation/CardinalityAggregation.php

src/Aggregation/ChildrenAggregation.php

src/Aggregation/DateRangeAggregation.php

src/Aggregation/ExtendedStatsAggregation.php

src/Aggregation/FilterAggregation.php

src/Aggregation/FiltersAggregation.php

src/Aggregation/GeoBoundsAggregation.php

src/Aggregation/GeoDistanceAggregation.php

src/Aggregation/GeoHashGridAggregation.php

src/Aggregation/GlobalAggregation.php

src/Aggregation/HistogramAggregation.php

src/Aggregation/Ipv4RangeAggregation.php

src/Aggregation/MaxAggregation.php

src/Aggregation/MinAggregation.php

src/Aggregation/MissingAggregation.php

src/Aggregation/NestedAggregation.php

src/Aggregation/PercentileRanksAggregation.php

src/Aggregation/PercentilesAggregation.php