Various docs about UFO, ROOF, and further plans

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-Architecture
-===========
- - Current implementation follows UFO architecture: reader and dataset-builder are split in two filters.
-  * The reader is multi-threaded. However, only a single instance of the builder is possible to schedule.
-  This could limit maximum throughput on dual-head or even signle-head, but many-core systems.
-  * Another problem here is timing. All events in the builder are initiaded from the reader. Consequently,
-  as it seems we can't timeout on semi-complete dataset if no new data is arriving.
-  * Besides, performance this is also critical for stability. With continuous streaming there is no problem,
-  however, if a finite number of frames requested and some packets are lost, the software will wait forever
-  for missing bits.
-
-
-Problems
-========
- - When streaming at high speed (~ 16 data streams; 600 Mbit & 600 kpck each), the data streams quickly get
- desynchronized (but all packets are delivered).
-    * It is unclear if problem is on the receiver side (no overloaded CPU cores) or de-synchronization is first
-    appear on the simmulation sender. The test with real hardware is required.
-    * For border case scenarios, increasing number of buffers from 2 to 10-20 helps. But at full speed, even 1000s
-    buffers are not enough. Packets counts are quickly going appart.
-    * Further increase of packet buffer provided to 'recvmmsg' does not help (even if blocking is enforced until 
-    all packets are received)
-    * At the speed specified above, the system works also without libvma.
-    * Actually, with libvma a larger buffer is required. In the beginning the performance of libvma is gradually 
-    speeding up (that was always like that). And during this period a significant desynchronization happens. To
-    compensate it, we need about 400 buffers with libvma as compared to only 10 required if standard Linux 
-    networking is utilized.
- - In any case (LibVMA or not), some packets will be lost in the beginning if high-speed communication is tested.
-    * Usually, first packets are transferred OK, but, then, a few packets will be lost occasionally here and there
-    (resulting in broken frames). This basically breaks grabbing a few packets and exitig. Unclear if server- or 
-    client-side problem (makes sense to see how real-hardware will behave).
-    * Can we pre-heat to avoid this speeding-up problem (increase pre-allocated buffers, disable power-saving 
-    mode, ??) Or it will be also not a problem with hardware? We can send UDP packets (should be send from another
-    host), but packets are still lost:
-        for i in $(seq 4000 4015); do echo "data" > /dev/udp/192.168.34.84/$i; done
-    * The following doesn't help: new version of libvma, tunning of the options.
- - Communication breaks with small MTU sizes (bellow 1500), but this is probably not important (Packets are 
- delivered but with extreme latencies. Probably some tunning of network stack is required).
- - Technically, everything should work if we start UFO server when data is already streamed. However, the first
- dataset could be any. Therefore, the check fails as the data is shifted by a random number of datasets.
-
-
-Questions
-=========
- - Can we pre-allocate several UFO buffers for forth-comming events. Currently, we need to buffer out-of-order
- packets and copy them later (or buffer everything for simplicity). We can avoid this data copy if we can get
- at least one packet in advance.
-
- - How I can execute 'generate' method on 'reductor' filter if no new data on the input for the specified 
- amount of time. One option is sending empty buffer with metadata indicating timeout. But this is again 
- hackish.
-
- - Can we use 16-bit buffers? I can set dimmensions to 1/4 of the correct value to address this. But is it
- possible to do in a clean way?
- 
- - What is 'ufotools' python package mentioned in documentation? Just a typo?