Resillience - avoid crashing in low-memory situations

[totto]

From long-time observations running uas on small aws instances, we can see that i dies

There is insufficient memory for the Java Runtime Environment to continue.
Native memory allocation (mmap) failed to map 12288 bytes for committing reser
ved memory.
Possible reasons:
The system is out of physical RAM or swap space
In 32 bit mode, the process size limit was hit
Possible solutions:
Reduce memory load on the system
Increase physical memory or swap space
Check if swap backing store is full
Use 64 bit Java on a 64 bit OS
Decrease Java heap size (-Xmx/-Xms)
Decrease number of Java threads
Decrease Java thread stack sizes (-Xss)
Set larger code cache with -XX:ReservedCodeCacheSize=
This output file may be truncated or incomplete.

Out of Memory Error (os_linux.cpp:2627), pid=18925, tid=140438209091328

We should handle this better...