Remove usage of Implementation-Build manifest entry to qualify initialize items for reload and deprecate reload-on-startup property

In combination with a hippo:version property, the hippo:reload-on-startup property is redundant. It is only relevant in combination with the module-wide version number stored in the Implementation-Build manifest entry.

Since to enable reload of an item that is newer based on the Implementation-Build manifest entry, you have to specify reload-on-startup anyway, so why not simply specify a hippo:version value? That is why we can get rid module-wide extension build version number.

Project that want certain items to always reload on a new deploy can use property interpolation and maven resource filtering to automatically set the hippo:version properties in an extension file.

The Implementation-Build manifest entry will still be read and set as the property hippo:extensionbuild for logging purposes only.