Fix post-install Script

[schlusslicht]

This pull request introduces some minor changes to the post-install.xql, allowing it to run against different Exist-DB versions and setup conditions. This is done by conditionally creating all necessary collections the application needs. Under, e.g., Exist-DB v6.2.0, the collection /db/system/config/db/apps does not exist, initially, whereby the original post-install.xql script fails, as it assumes the existence of the /db/system/config/db/apps collection.

Furthermore, if the application is deployed for the first time (into a fresh Exist-DB instance for example), the collections /db/apps/pessoa/data and /db/apps/pessoa/data/{doc,pub} do not yet exist, wherefore the original post-install.xql script also fails, as it assumes the existence of those collections.

By introducing a conditional and recursive mkcol function and calling it with the full $path of all necessary collections, all different scenarios (e.g., different Exist-DB versions, as well as, arbitrary deployment counts) should be caught and handled correctly.