Add option to change the number of entries per page (fixes #40)

api/payload.go

client/core.go

database/migration.go

database/sql.go

database/sql/schema_version_32.sql

locale/translations.go

locale/translations/de_DE.json

locale/translations/en_US.json

locale/translations/es_ES.json

locale/translations/fr_FR.json

locale/translations/it_IT.json

locale/translations/ja_JP.json

locale/translations/nl_NL.json

locale/translations/pl_PL.json

locale/translations/ru_RU.json

locale/translations/zh_CN.json

model/user.go

storage/user.go

template/html/settings.html

template/views.go