#80 created class GeschaeftsberichtBranchenAmounts

GeschaeftsberichtBranchenAmounts is a serversearch which fetches the
amounts of branchen for customers.
 #80 GeschaeftsberichtBranchenAmounts executes 3 queries

The serversearch GeschaeftsberichtBranchenAmounts provides results for
three queries.
 #80 added fetch for the Umsatz

GeschaeftsberichtBranchenAmounts can now fetch the Umsatz. As it returns
a Double, the number field in the used Bean was set to the type Number.
 #80 added the other queries
 #80 renamed server search

Renamed GeschaeftsberichtBranchenAmounts to
BillingStatisticsReportServerSearch and added some comments.
Merge branch 'feature/80-charts-Geschäftsstatistik' into dev