Add support for session-cache in config file and as cmdline option

[ingvarha]

[ingvar@centos7 ~]$ hitch --version
hitch 1.4.4

[ingvar@centos7 ~]$ hitch --help | grep session-cache
-C --session-cache=NUM Enable and set SSL session cache to specified number

[ingvar@centos7 ~]$ hitch --session-cache=100 default.example.com.pem
hitch: unrecognized option '--session-cache=100'
hitch: unrecognized option '--session-cache=100'
Invalid command line parameters. Run hitch --help for instructions.

[ingvar@centos7 ~]$ echo -e "pem-file="$(pwd)/default.example.com.pem"\nsession-cache=100" > hitch.conf
[ingvar@centos7 ~]$ hitch --config=hitch.conf
parsing error: line: 2: syntax error

[ingvar@centos7 ~]$ hitch -C 100 default.example.com.pem
20170208T141938.453163 [ 2611] {core} hitch 1.4.4 starting
20170208T141938.453334 [ 2611] {core} Using OpenSSL version 1000105f.
20170208T141938.457479 [ 2611] {core} Listening on 0.0.0.0:8443
20170208T141938.457545 [ 2611] {core} Listening on [::]:8443
20170208T141938.457555 [ 2611] {core} Loading certificate pem files (1)
(...)