Validate num_threads setting.
Validate num_threads setting.

Previously SequenceServer would assume 1 thread if num_threads wasn't set, or
set incorrectly in the config file. I think we should use a default value only
if one wasn't provided by the user. If the user explicitly sets a configuration
value, and it's incorrect, we should alert the user instead. Additionally, we
warn the user if num_threads is greater than 256.

Explicit validation caught an error in our code where num_threads, if not set
in config file, was assumed to be 0 in Ruby 1.8.7.

Signed-off-by: Anurag Priyam <6e6ab5ea9cb59fe7c35d2a1fc74443577eb60635@gmail.com>

elsiklab/sequenceserver,lepbase/lepbase-sequenceserver,deepakunni3/sequenceserver,deepakunni3/sequenceserver,vivekiitkgp/sequenceserver,yeban/sequenceserver,yeban/sequenceserver,aldermossy/sequenceserver,elsiklab/sequenceserver,aldermossy/sequenceserver,aldermossy/sequenceserver,IsmailM/sequenceserver,yeban/sequenceserver,lepbase/lepbase-sequenceserver,deepakunni3/sequenceserver,jasminZ/sequenceserver,jasminZ/sequenceserver,IsmailM/sequenceserver,lepbase/lepbase-sequenceserver,IsmailM/sequenceserver,elsiklab/sequenceserver,vivekiitkgp/sequenceserver,jasminZ/sequenceserver,vivekiitkgp/sequenceserver,yeban/sequenceserver,aldermossy/sequenceserver