[BUGFIX] Log exceptions recursively in ``SystemLogger::logException()``
[BUGFIX] Log exceptions recursively in ``SystemLogger::logException()``

With this change "post mortem" information about the complete exception
chain is logged, and not only for the outer exception.

This also adds some cosmetic and non-functional cleanups in order to
increase readability and IDE support:

* Import FQN where applicable
* Remove unused import statements

Change-Id: I43eddfd5b5b978afce64ec7ff43f414444680672
Releases: master, 2.3, 2.2
Fixes: FLOW-159
Original-Commit-Hash: 38602eb9d09ee6ad87a74352eadfaa17312d547c

neos/flow-development-collection,robertlemke/flow-development-collection,albe/flow-development-collection,gerhard-boden/flow-development-collection,albe/flow-development-collection,fcool/flow-development-collection,fcool/flow-development-collection,chewbakartik/flow-development-collection,kitsunet/flow-development-collection,dlubitz/flow-development-collection,mkeitsch/flow-development-collection,aertmann/flow-development-collection,kdambekalns/flow-development-collection,gerhard-boden/flow-development-collection,kitsunet/flow-development-collection,chewbakartik/flow-development-collection,daniellienert/flow-development-collection,dlubitz/flow-development-collection,mkeitsch/flow-development-collection,bwaidelich/flow-development-collection,aertmann/flow-development-collection,fcool/flow-development-collection,dfeyer/flow-development-collection,robertlemke/flow-development-collection,dfeyer/flow-development-collection,daniellienert/flow-development-collection,robertlemke/flow-development-collection,gerhard-boden/flow-development-collection,dlubitz/flow-development-collection,neos/flow-development-collection,chewbakartik/flow-development-collection,daniellienert/flow-development-collection,bwaidelich/flow-development-collection,bwaidelich/flow-development-collection,dfeyer/flow-development-collection,neos/flow-development-collection,kdambekalns/flow-development-collection,kdambekalns/flow-development-collection,neos/flow-development-collection,fcool/flow-development-collection,mkeitsch/flow-development-collection,dfeyer/flow-development-collection,albe/flow-development-collection,kitsunet/flow-development-collection,robertlemke/flow-development-collection,aertmann/flow-development-collection,kdambekalns/flow-development-collection