Update IPFIX DB writer config

Use separate element to store database type instead of specifying it in
the <ipfixDbWriter>'s name.
Merge branch 'master' into update_dbwriter_config
Adapt config files to use ipfixDbWriter

The config file tag <ipfixDbWriterMySQL> changed to <ipfixDbWriter> with
a <dbType> subtag.
Remove ipAddressType from config files

The <ipAddressType> tag inside the <collector> tag is not valid for
an <ipfixExporter>.
Merge branch 'update_dbwriter_config'