postinst handling depends on order in control file

[phako]

we are using plain "postinst" name. This causes debhelper to attach the postinst to the first package in the control file. which makes it a bit random to which package the postinst is attached to

[phako]

Proposal:

• Update the current script to handle the debian packaging scripts with the respective package prefixes, such as bin.postinst, extra.prerm, ...
• The prefixes (bin, extra, ... ) are replaced by the actual package name to help debhelper associating the file corrctly
• If any of the packaging scripts exists without any prefix and there are more than one packages to be built, assume it is used for the (doocs-)bin package