Nov sprint

The following commits add support for handling avro encoded sync files during calculation init.

lib/calculate.sh script is responsible for initializing pig computations. 

calculate.sh prepares the following sync files and passes them as parameters to pig latin calculation script:
 - poem_sync
 - sites_sync
 - downtimes_sync
 - hepspec_sync

An additional configuration parameter has been added in /etc/ar-compute-engine.conf : serialization
if serialization=avro then the avro serialization framework has been enabled 
if serialization=none then flat delimited text files are being used 

calculate.sh now checks for the status of serialization config parameter.
If serialization=none then calculate.sh operates as it used to by handling the flat text files
If serialization=avro then calculate.sh looks for the avro encoded sync files (.avro extension) and calls the corresponding decoders (in /usr/libexec/lib/avro) 

The decoders include:
../lib/avro/poem_decode.py -- decoder for poem_sync avro files
../lib/avro/downtimes_decode.py -- decoder for downtimes_sync avro files
../lib/avro/sites_decode.py -- decoder for downtimes_sync avro files
../lib/avro/hepspec_decode.py -- decoder for hepspec_sync avro files

The decoders currently use the minimal fields of the schema files + some additional fields (egi specific) when necessary:

More specifically:

hepspec_decode retrieves the following schema fields:
[ 'site', 'weight' ]

downtimes_decode retrieves the following schema fields:
['hostname', 'service', 'start_time', 'end_time']

poem_decode retrieves the following schema fields:
['name', 'service', 'metric', 'vo' ] -- vo is additional (egi specific) field 

poem_decode retrieves the following schema fields:
[hostname','service','production','monitored','scope','site','roc','infrastructure','certification','site_scope']
-- production,monitored,scope,roc,infrastructure,certification,site_scope are additional (egi specific) fields

The avro encoded data of the consumer files doesn't concern calculate.sh since it passes through the prefilter script and the prefilter output (non-encoded) is placed directly to hive database (when in cluster mode) or to prefilter.out text file (when in local mode)
If we are "decoding" the file to the previous ascii format, why do we use avro in the first place?